The influx of serum albumin to enamel matrix in rat incisors after trauma

The most frequent results of trauma to tooth germs are enamel hypoplasia and enamel hypocalcification. These differing results may be due to the stage of amelogenesis at which trauma occurs. The cellular and biomolecullar events involved in the genesis of these defects are poorly understood. We hypothesized that one factor involved is the possibility that relatively high levels of serum albumin enter the enamel matrix through the damaged enamel organ, and impair mineralization of the matrix. The present study was undertaken to immunohistochemically and autoradiographically localize serum albumin in the enamel organs of rat incisors after trauma was inflicted to the mandibular incisor region of 4-day-old rats. Hemorrhage was seen surrounding the enamel organ and between the detached secretory-stage ameloblasts. One day after trauma, the most intense immunohistochemical (IHC) staining for albumin was localized in the outer layer of the enamel matrix adjacent to the detached secretory-stage ameloblasts. Albumin was also detected autoradiographically in the secretory-stage ameloblasts layer and enamel matrix. These findings indicate that serum albumin can leak between the detached ameloblasts and penetrate the enamel matrix after trauma. Leaked albumin was still present in the matrix during the maturation stage. Leaked albumin in the developing enamel could inhibit crystal growth and result in hypocalcification.

In vitro and in vivo properties of recombinant human serum albumin from Pichia pastoris purified by a method of short processing time

PURPOSE

Recombinant human serum albumin (rHSA), secreted by a Pichia pastoris expression system, was purified by a fast and efficient method, the essential feature of which is strong but reversible binding of the protein to Blue Sepharose. The structural characteristics, stability, and ligand-binding properties of the resulting protein were examined, and pre-clinical studies were performed.

METHODS

Protein structure was investigated by amino acid sequencing, sodium polyacrylamide gel electrophoresis, CD spectroscopy and chromatography. Stability was examined by denaturation by guanidine hydrochloride and by calorimetry, and ligand binding was studied by ultrafiltration. Rat experiments were performed with 125I-labeled albumin.

RESULTS

Far-ultraviolet and near-ultraviolet CD spectra of rHSA were identical to those of human serum albumin isolated from serum (HSA). Mercaptalbumin and non-mercaptalbumin were separated by high-performance liquid chromatography using an N-methylpyridinium polymer-based column. 60% of rHSA existed as mercaptalbumin, a content that is higher than that of a commercial preparation of HSA. Fatty acids, N-acetyl-L-tryptophan and pasteurization had similar effects on the conformational stability of rHSA and HSA. Stereoselective ligand-binding properties (warfarin, phenprocoumon, pranoprofen and ibuprofen) of rHSA were the same as those of HSA. The effect of the neutral to base transition on warfarin (site I-ligand) and dansylsarcosine (site II-ligand) binding to rHSA was also similar to HSA. In vivo studies showed comparable half-lives, excretion and tissue distributions of the two albumin preparations.

CONCLUSION

The present yeast expression system and purification procedure result in rHSA with structural and functional properties very similar to those of HSA.

[Effect of experimentally induced trauma to the incisors in rats]

The purpose of this study was to produce developmental lesions of enamel in rats by a quick and simple method and to examine the enamel hypoplasia caused by trauma. 4-day-old and 3-week-old Wistar rats were used. Trauma was produced by needle pricking and hitting on the mandibula. After one week incisors were removed together with jaws and prepared for microradiography, X-ray diffraction, light microscope and transmission electron microscope examination. Microradiographic findings in the needle pricking group revealed hypocalcified and hypoplastic enamel. The incidence was 73.7%. In the hitting group of 4-day-old rats the incidence was lower, 70.0%. Microradiographic findings in this group were diffuse hypoplasia in the surface enamel. Hitting of 3-week-old rats produced no enamel hypoplasia. Crystallinity of hypoplastic enamel was reduced in both a-axis and c-axis direction. Histological findings in 4-day-old rats revealed disarranged and detached ameloblasts at location trauma. These results indicate that a needle pricking method involving secretory stage ameloblasts of 4-day-old rat incisors can induce a considerable amount of enamel hypoplasia.

Human CC chemokine liver-expressed chemokine/CCL16 is a functional ligand for CCR1, CCR2 and CCR5, and constitutively expressed by hepatocytes

Liver-expressed chemokine (LEC)/CCL16 is a human CC chemokine selectively expressed in the liver. Here, we investigated its receptor usage by calcium mobilization and chemotactic assays using mouse L1.2 pre-B cell lines stably expressing a panel of 12 human chemokine receptors. At relatively high concentrations, LEC induced calcium mobilization and chemotaxis via CCR1 and CCR2. LEC also induced calcium mobilization, but marginal chemotaxis via CCR5. Consistently, LEC was found to bind to CCR1, CCR2 and CCR5 with relatively low affinities. The binding of LEC to CCR8 was much less significant. In spite of its binding to CCR5, LEC was unable to inhibit infection of an R5-type HIV-1 to activated human peripheral blood mononuclear cells even at high concentrations. In human liver sections, hepatocytes were strongly stained by anti-LEC antibody. HepG2, a human hepatocarcinoma cell line, was found to constitutively express LEC. LEC was also present in the plasma samples from healthy adult donors at relatively high concentrations (0.3--4 nM). Taken together, LEC is a new low-affinity functional ligand for CCR1, CCR2 and CCR5, and is constitutively expressed by liver parenchymal cells. The presence of LEC in normal plasma at relatively high concentrations may modulate inflammatory responses.

Conformational stability and warfarin-binding properties of human serum albumin studied by recombinant mutants

Correctly folded recombinant wild-type human serum albumin and the single-residue mutants K199A, W214A, R218H and H242Q were produced with the use of a yeast expression system. The changes in R218H resulted in a pronounced decrease in intrinsic fluorescence. Thermodynamic parameters for thermal denaturation of the present mutants and of five additional mutants have been determined, showing small increases in stability for two mutants (R218H and H242Q) and a larger decrease in stability for one (W214A). In the last of these, denaturation was a heterogeneous process starting at physiological temperature. The high-affinity binding constant for warfarin at pH 7.4 was determined by fluorescence spectroscopy: there was a significant increase in affinity for binding of warfarin to H242Q and K199A and a smaller decrease in affinity for W214A and R218H. The findings show that Trp-214 is not as essential for the high-affinity binding of warfarin as has previously been thought.

The immunohistochemical localization of Bax and Bcl-2 and their relation to apoptosis during amelogenesis in developing rat molars

Bax and Bcl-2 are members of a family of intracellular, membrane-associated proteins that regulate programmed cell death. It has been suggested that, when Bax predominates, programmed cell death is accelerated and the apoptosis inhibitory activity of Bcl-2 is suppressed. The present study was undertaken to immunohistochemically (IHC) localize Bax and Bcl-2 in the cells of the enamel organ during amelogenesis in rat molars. Also, apoptotic cells were detected by TUNEL staining. The IHC intense localization of Bcl-2 and light staining for Bax in the pre-ameloblasts suggest that apoptosis is inhibited in the proliferating pre-ameloblasts. This is consistent with an absence of TUNEL staining for apoptosis in these cells. However, in the late secretory and transition ameloblasts, and adjacent stratum intermedium, evidence of apoptosis of the ameloblasts was observed. Bax and Bcl-2 were co-localized in the proximal ends of late secretory, transition and early maturation-stage ameloblasts, but immunoreactivity for Bax markedly increased in the proximal ends of late secretory and transition ameloblasts, while the Bcl-2 staining appeared to be lighter. This suggests that Bax antagonized Bcl-2 function, limiting the ability of Bcl-2 to prolong cell survival. In the early maturation stage, Bax staining faded while the immunoreactivity for Bcl-2 increased. Evidence of distinct apoptosis was reduced in the early maturation stage ameloblasts. When related to the occurrence of apoptosis during amelogenesis, the relative intensity of expression of Bax and Bcl-2 changed in a pattern consistent with that observed in other cell lines. This indicates that these proteins play essential roles in the process of amelogenesis, as predicted by their proposed mechanisms of action in the control of apoptosis.

Apoptotic cells of an epithelial cell line, AsPC-1, release monocyte chemotactic S19 ribosomal protein dimer

A pancreatic carcinoma cell line, AsPC-1, underwent apoptosis in vitro when heat-treated for 60 min at 43 degrees C. Apoptotic AsPC-1 cells liberated a monocyte chemotactic factor into the culture supernatant 24 to 30 h after the heat-treatment. This factor was immunologically identified as the cross-linked homodimer of S19 ribosomal protein (RP S19), since the majority of the chemotactic activity was absorbed by both anti--RP S19 rabbit antibodies and an anti--isopeptide bond monoclonal antibody immobilized on agarose beads. Intracellular transglutaminase activity increased during the apoptotic process, reaching the peak strength between 18 and 24 h after the heat-treatment. A recombinant RP S19 acquired the monocyte chemotactic capacity when incubated with the apoptotic cell extract obtained at the 18th hour. The chemotactic activity acquirement as well as the transglutaminase activity were blocked by treatment of the extract with anti--type II transglutaminase rabbit antibodies. When the recombinant RP S19 was treated with an authentic type II transglutaminase, the dimerization of RP S19 concomitant with the generation of the monocyte chemotactic activity was observed. Peptide-map analyses involving amino acid sequencing demonstrated that the inter-molecular isopeptide bond was heterogeneous: Gln12 or Gln137 and Lys29 or Lys122 were cross-linked. Site-directed mutagenic analysis indicated that the cross-linking of Gln137, but not other residues such as Gln12, Lys29, and Lys122, was essential for expression of the chemotactic activity.

Activation of blood coagulation factor IX by gingipains R, arginine-specific cysteine proteinases from Porphyromonas gingivalis

The effect of two arginine-specific cysteine proteinases (gingipains R) from Porphyromonas gingivalis, an aetiological factor of adult periodontitis, on the activation of human factor IX was investigated in the presence of ethylene glycol, an activity enhancer of activated factor IX (factor IXa), with the use of a fluorogenic oligopeptide substrate. Each gingipain R rapidly activated factor IX but the 95 kDa proteinase complex (HRgpA) that contains both haemagglutinin/adhesion and catalytic domains was 2.4-fold more efficient than the single-chain 50 kDa gingipain R (RgpB), which has only a catalytic domain. SDS/PAGE and N-terminal sequence analysis of factor IX digestion fragments indicated that, like all endogenous activators, gingipains R also produce factor IXabeta via an IXa intermediate. Significantly, phospholipids augmented the activation of factor IX by HRgpA but not by RgpB in a Ca(2+)-dependent manner. In the presence of both cofactors the kinetic efficiency of HRgpA to activate factor IX (k(cat)/K(m)=1.9x10(6) M(-1).s(-1)) was 8.5-fold higher than that of RgpB (k(cat)/K(m)=2.3x10(5) M(-1).s(-1)) and double that of the factor VIIa-tissue factor complex, but 8-fold lower than that for factor XIa. A comparison of the relative activation rates of factor IX, factor X and prothrombin directly in plasma by HRgpA suggests a significant contribution for factor IX conversion in blood coagulation induced by gingipains R. Taken together, gingipains R are the first-reported activators of factor IX of bacterial origin. By this effect they could be involved in the production of thrombin as well as the subsequent generation of prostaglandins and interleukin 1, all of which have been found to be associated with the development and progression of periodontitis.

Role of arg-410 and tyr-411 in human serum albumin for ligand binding and esterase-like activity

Recombinant wild-type human serum albumin (rHSA), the single-residue mutants R410A, Y411A, Y411S and Y411F and the double mutant R410A/Y411A were produced using a yeast expression system. The recombinant proteins were correctly folded, as they had the same stability towards guanidine hydrochloride and the same CD spectrum as HSA isolated from serum (native HSA). Thus the global structures of the recombinant proteins are probably very similar to that of native HSA. We investigated, by ultrafiltration and CD, the high-affinity binding of two representative site II ligands, namely ketoprofen and diazepam. According to the crystal structure of HSA, the residues Arg-410 and Tyr-411 protrude into the centre of site II (in subdomain 3A), and the binding results showed that the guanidino moiety of Arg-410, the phenolic oxygen and the aromatic ring of Tyr-411 are important for ketoprofen binding. The guanidino moiety probably interacts electrostatically with the carboxy group of ketoprofen, the phenolic oxygen could make a hydrogen-bond with the keto group of the ligand, and the aromatic ring may participate in a specific stacking interaction with one of or both of the aromatic rings of ketoprofen. By contrast, Arg-410 is not important for diazepam binding. The two parts of Tyr-411 interact favourably with diazepam, and probably do so in the same way as with ketoprofen. In addition to its unique ligand binding properties, HSA also possesses an esterase-like activity, and studies with p-nitrophenyl acetate as a substrate showed that, although Arg-410 is important, the enzymic activity of HSA is much more dependent on the presence of Tyr-411. A minor activity could be registered when serine, but not alanine or phenylalanine, was present at position 411.

Primary structure of guinea pig plasma prekallikrein

A full length guinea pig plasma prekallikrein (PK) cDNA was cloned from a liver cDNA library. The nucleotide sequence with 2242 bp was analyzed and the amino acid sequence with 618 residues was deduced. Kallikrein was purified from guinea pig plasma and cleavage site in the activation was determined. The amino acid sequence around the cleavage site -368Ile-Asp-Ala-Arg-Ile-Val-Gly-375Gly- differed from that of the human PK -368Thr-Ser-Thr-Arg-Ile-Val-Gly-375Gly-. Protease substrates containing penta-peptides which mimicked the sequence of the cleavage sites from P3 to P2' of guinea pig Hageman factor (HF) and PK were synthesized, and kinetic analyses of the hydrolysis by guinea pig activated HF (HFa) and kallikrein were carried out. The combination between HFa and the PK mimicking peptide provided the best kinetics. These results in part explain why the cascade activation of PK by HFa is predominant in the guinea pig system.

Determination of the cross-linked residues in homo-dimerization of S19 ribosomal protein concomitant with exhibition of monocyte chemotactic activity

When S19 ribosomal protein molecules are intermolecularly cross-linked by a transglutaminase-catalyzed reaction, the monocyte chemotactic activity is newly expressed. Heparin, at a concentration of 1 U/ml, greatly augmented the cross-linking reaction. This augmentation was due to binding affinity of S19 ribosomal protein to heparin. The major heparin-binding region of S19 ribosomal proteins was identified to Lys23-Lys-Ser-Gly-Lys-Leu-Lys29, using region-directed mutant proteins. The amino acid residues of S19 ribosomal protein used for the intermolecular cross-linkage were then determined by the peptide map analysis with amino acid sequencing and by the site-directed mutagenesis; Gln137 and Lys122 were used in the intermolecular cross-linkage.

Organization of the chemokine gene cluster on human chromosome 17q11.2 containing the genes for CC chemokine MPIF-1, HCC-2, HCC-1, LEC, and RANTES

To understand the organization of the human CC chemokine gene cluster on chromosome 17q11.2, we determined the nucleotide sequence of a region 181 kb long containing five CC chemokine genes, MPIF-1 (SCYA23), HCC-2 (SCYA15), HCC-1 (SCYA14), LEC (SCYA16), and RANTES (SCYA5), by the random shot-gun method. The four CC chemokine genes, MPIF-1, HCC-2, HCC-1, and LEC, are clustered within a region 40 kb long, whereas the RANTES gene is located approximately 10 kb apart from the four chemokine gene minicluster. These chemokine genes are arranged in the same orientation, and their sizes are relatively long, 3.1 (HCC-1)-8.8 kb (RANTES) when compared with other CC chemokine genes, such as MIP-1alpha/LD78alpha (SCYA3) (1.9 kb) and MCP-1 (SCYA2) (1.5 kb). In contrast to most other human CC chemokine genes that consist of three exons, the MPIF-1 and HCC-2 genes, separated by 12 kb, have four exons. When the nucleotide sequences of the MPIF-1 and HCC-2 genes are compared, they are well conserved, including introns and flanking sequences, except for the middle region of the long first intron, indicating that they have been generated recently in evolutionary terms by duplication. In addition to the CC chemokine genes, more than 30 exons are identified in the sequenced region by similarity search against expressed sequence tags (ESTs) and also by the gene prediction program GenScan. This indicates that the chemokine cluster sequenced in this study is a gene-rich region in the human genome.

The immunohistochemical localization of the interferon-gamma and granulocyte colony-stimulating factor receptors during early amelogenesis in rat molars

Previous studies, in which the known janus kinase and signal transducer and activator of transcription (STAT) isoforms were immunohistochemically mapped in developing rat molars, implicated a sizeable list of cytokine superfamily receptor (CSR)/signal-transduction pathway (STP) linkages in the cells of the enamel organ involved in the events leading directly to early amelogenesis. Various combinations of upregulated janus kinases and STATs are known to be linked to single or small groups of CSRs. On the basis of the previous observations it was hypothesized that the interferon-gamma receptor (IFNgamma r) and the granulocyte colony-stimulating factor receptor (G-CSF receptor) would be localized in specific sites in the cells of the enamel organ during early amelogenesis. To verify this, whole-head, freeze-dried sections were here obtained at the level of the mandibular first and second molar from newborn and 5-day-old rats. These sections were not demineralized or fixed, reducing the possibility of false-negative results. Antibodies to the IFNgamma r and the G-CSF receptor were localized using a modification of the avidin-biotin complex method. In the newborn rats, IFNgamma r was localized in the preameloblasts in the cervical loop, the proximal and distal ends of presecretory ameloblasts, the outer enamel epithelium, the dental lamina, and in bone. In 5-day-old rats, it was confined to the proximal ends of the presecretory and secretory ameloblasts. The G-CSF receptor was observed in the molars of newborn rats in the preameloblasts, the proximal and distal ends of the presecretory ameloblasts, outer enamel epithelium, and in bone. In 5-day-old rats, G-CSF receptor was localized in the preameloblasts, the proximal ends of presecretory and secretory ameloblasts, the stellate reticulum, the outer enamel epithelium, and in bone. These findings indicate that the IFNgamma r and the G-CSF receptor, and their downstream STP linkages, are upregulated in the cells of the enamel organ and may be involved in the events leading directly to early enamel formation.

Production and regulation of monocyte chemoattractant protein-1 in lipopolysaccharide- or monosodium urate crystal-induced arthritis in rabbits: roles of tumor necrosis factor alpha, interleukin-1, and interleukin-8

The production of monocyte chemoattractant protein-1 (MCP-1) and its regulation by TNFalpha, IL-1, and IL-8 were investigated in two rabbit models of arthritis induced by intra-articular injection of lipopolysaccharide (LPS) or monosodium urate (MSU) crystals. We first prepared recombinant rabbit MCP-1 and antibodies and then developed an immunoassay. The immunoassay detected 3 pg/ml rabbit MCP-1 and did not cross-react with other rabbit chemokines such as IL-8 or GRO. MCP-1 was first detected in synovial fluid (SF) at 1 hour, and peaked at 4 or 2 hours after the injection of LPS or MSU crystals, respectively. Immunohistochemically, MCP-1 was detected in synovial lining cells and infiltrating neutrophils. The amounts of MCP-1 detected in SF from neutrophil-depleted rabbits were similar to those in normal rabbits, suggesting that synovial lining cells were the main source of MCP-1 detected in SF. The peak level of MCP-1 in SF after LPS-injection was inhibited by 57% with anti-TNFalpha mAb and by 41% with IL-1 receptor antagonist (IL-1Ra). Coadministration of anti-TNFalpha mAb and IL-1Ra inhibited 90% of MCP-1 production. In contrast, the peak level of MCP-1 in SF after MSU crystal-injection was not affected by any cytokine inhibitor, but was reduced by 52% with coadministration of anti-TNFalpha mAb and IL-1Ra. Anti-IL-8 IgG had no effect on the production of MCP-1 in either model. Thus, the production of MCP-1 in LPS-induced arthritis was mostly regulated by TNFalpha and IL-1, whereas half the extent of MCP-1 production in MSU crystal-induced arthritis was independent of TNFalpha or IL-1. IL-8 does not seem to regulate the production of MCP-1 in SF either directly or indirectly. Finally, administration of neutralizing anti-MCP-1 antibody inhibited LPS- and MSU crystal-induced monocyte infiltration by 58.4% and 44.9%, respectively, suggesting that synovial production of MCP-1 plays an important role in the recruitment of monocytes in these arthritis models.

Reversed-phase ion-pair chromatographic analysis of tetracycline antibiotics. Application to discolored teeth

A high-performance liquid chromatographic method with diode array detection was developed to simultaneously separate tetracycline antibiotics and applied to the analysis of discolored teeth. By a reversed-phase ion-pair chromatographic system using pentanesulfonate as a counter ion, minocycline, oxytetracycline, tetracycline and demeclocycline were eluted in this order, and they showed base-line separation within 9 min. When using oxytetracycline as an internal standard, the quantitative ranges were between 2.5 ng/ml and 7.5 microg/ml. Powdered dentine (10 mg) and enamel (40 mg) prepared from discolored primary teeth were sonicated in 0.25 ml of 10 mM HCl containing oxytetracycline (0.75 microg/ml) and 50 mM EDTA-2Na, thereafter the supernatants were chromatographed. Eluates from both discolored tooth samples were identified as minocycline based on diode array spectra of their peaks, while minocycline was not detected in any samples from nondiscolored normal teeth, indicating that discoloration of the tested teeth was due to minocycline incorporated into dentine and enamel. Replicate quantitative analyses of the identical tooth substances showed that intra- and inter-assay C.V.s were 2.63 and 4.95% for dentine, and 5.42 and 10.88% for enamel. Application of the developed method to nine discolored teeth revealed that the incorporated minocycline ranged from 20.13 to 84.62 ng/mg of dentine and 0.89 to 7.87 ng/mg of enamel.

The ornithine transcarbamylase (OTC) gene: mutations in 50 Japanese families with OTC deficiency

Mutations in the OTC gene in 50 Japanese families with OTC deficiency were reviewed in relation to the phenotype of the patients and predicted structure of the mutant enzyme. Similar to other X-linked diseases, mutant alleles in OTC deficiency are highly heterogeneous. Mutations observed in male patients with neonatal onset of the disease included base insertion/deletion, exon skipping, and nonsense and missense mutations in exon 4, 5, 6, or 7. OTC activity was essentially undetectable in this group of patients. These mutations possibly resulted in unstable mRNA or truncated protein, or involved the active site or core domain of the enzyme leading to structural changes. In male patients with late onset, abnormalities observed were missense mutations in exons 2, 4, 8, 9, and 10, and missense mutations plus donor site errors involving exons 4, 5, and 6. OTC activity in these patients was 8.1 +/- 6.3% of the control and most mutations occurred on the surface of the protein. In female patients, age at onset ranged from 19 months to 7 years, depending on residual OTC activities (4.5 to 33% of the control). Most mutations in this group were similar to those seen in male patients with neonatal onset, i.e., nonsense and missense mutations in exons 5 and 6, and exon skipping, leading to null enzyme activity. These collective data can serve for genetic counseling and monitoring in prenatal care.

Structural characterization of the gene and corresponding cDNA for the cytochrome P450rm from Rhodotorula minuta which catalyzes formation of isobutene and 4-hydroxylation of benzoate

Cytochrome P450rm was previously isolated from the basidiomycete yeast Rhodotorula minuta as a bifunctional enzyme with isobutene-forming and benzoate 4-hydroxylase activities. We cloned the gene and corresponding cDNA for P450rm in order to characterize the enzyme in the context of fungal phylogeny and physiology. From the cDNA sequence, P450rm was deduced to have 527 amino acids with a calculated molecular weight of 59136. P450rm shared 48% amino acid sequence identity with CYP53A1 from Aspergillus niger, indicating that the gene belongs to a novel subfamily of CYP53, CYP53B. However, the organization of the P450rm gene, which has eight exons and seven introns, differed completely to that of CYP53A1. Northern analysis demonstrated that the level of P450rm mRNA expression increased when L-phenylalanine was used as sole carbon source. These results suggest that P450rm has been well conserved during the evolution of fungi as a benzoate 4-hydroxylase in the dissimilation pathway starting from L-phenylalanine

Activation of blood coagulation factor X by arginine-specific cysteine proteinases (gingipain-Rs) from Porphyromonas gingivalis

The effect of two arginine-specific cysteine proteinases (gingipain Rs) from Porphyromonas gingivalis, a causative bacterium of adult periodontitis, on human blood coagulation was investigated. Activated partial thromboplastin time and prothrombin time were shortened by these proteinases, with a 95-kDa gingipain R containing adhesin domains being 5-fold more efficient in comparison to a 50-kDa gingipain R containing the catalytic domain alone. The 50-kDa enzyme reduced each coagulation time in several plasmas deficient in various coagulation factors, while it was ineffective in factor X-deficient plasma unless reconstituted with this protein. Each proteinase activated factor X in a dose- and time-dependent manner, with Michaelis constants (Km) being found to be lower than the normal plasma factor X concentration, strongly suggesting that factor X activation by gingipain Rs, especially the 95-kDa form which is strongly activated by phospholipids, could occur in plasma. This is the first report of factor X activation by bacterial proteinases and indicates that the gingipain Rs could be responsible for the production of thrombin and, indirectly, with the generation of prostaglandins, interleukin-1, etc., which have been found to be associated with the development of periodontitis induced by P. gingivalis infections. Furthermore, the data support the hypothesis that induction of blood coagulation by bacterial proteinases may be a causative agent in the pathogenesis of disseminated intravascular coagulation in sepsis.

Human glutamate pyruvate transaminase (GPT): localization to 8q24.3, cDNA and genomic sequences, and polymorphic sites

Two frequent protein variants of glutamate pyruvate transminase (GPT) (E.C.2.6.1.2) have been used as genetic markers in humans for more than two decades, although chromosomal mapping of the GPT locus in the 1980s produced conflicting results. To resolve this conflict and develop useful DNA markers for this gene, we isolated and characterized cDNA and genomic clones of GPT. We have definitively mapped human GPT to the terminus of 8q using several methods. First, two cosmids shown to contain the GPT sequence were derived from a chromosome 8-specific library. Second, by fluorescence in situ hybridization, we mapped the cosmid containing the human GPT gene to chromosome band 8q24.3. Third, we mapped the rat gpt cDNA to the syntenic region of rat chromosome 7. Finally, PCR primers specific to human GPT amplify sequences contained within a "half-YAC" from the long arm of chromosome 8, that is, a YAC containing the 8q telomere. The human GPT genomic sequence spans 2,7 kb and consists of 11 exons, ranging in size from 79 to 243 bp. The exonic sequence encodes a protein of 495 amino acids that is nearly identical to the previously reported protein sequence of human GPT-1. The two polymorphic GPT isozymes are the results of a nucleotide substitution in codon 14, coding for a histidine in GPT-1 and an asparagine in GPT-2, which causes a gain or loss of an NlaIII restriction site. In addition, a cosmid containing the GPT sequence also contains a previously unmapped, polymorphic microsatellite sequence, D8S421. The cloned GPT gene and associated polymorphisms will be useful for linkage and physical mapping of disease loci that map to the terminus of 8q, including atypical vitelliform macular dystrophy (VMD1) and epidermolysis bullosa simplex, type Ogna (EBS1). In addition, this will be a useful system for characterizing the telomeric region of 8q. Finally, determination of the molecular basis of the GPT isozyme variants will permit PCR-based detection of this world-wide polymorphism.

Activation of human matrix metalloproteinases by various bacterial proteinases

Matrix metalloproteinases (MMPs) are zinc-containing proteinases that participate in tissue remodeling under physiological and pathological conditions. To test the involvement of bacterial proteinases in tissue injury during bacterial infections, we investigated the activation potential of various bacterial proteinases against precursors of MMPs (proMMPs) purified from human neutrophils (proMMP-8 and -9) and from human fibrosarcoma cells (proMMP-1). Each proMMP was subjected to treatment with a series of bacterial proteinases at molar ratios of 0.01-0.1 (bacterial proteinase to proMMP), and activities of MMPs generated were determined. Among six different bacterial proteinases, thermolysin family enzymes (family M4) such as Pseudomonas aeruginosa elastase, Vibrio cholerae proteinase, and thermolysin strongly activated all three proMMPs via limited proteolysis to generate active forms of the MMPs. N-terminal sequence analysis of the active MMPs revealed that cleavage occurred at the Val82-Leu83 and Thr90-Phe91 bonds of proMMP-1 and proMMP-9, respectively, which are located near the N terminus of the catalytic domain of MMPs. In contrast, Serratia 56-kDa proteinase and Pseudomonas alkaline proteinase, both of which are classified as members of the serralysin subfamily of zinc metalloproteinases (family M10), and Serratia 73-kDa thiol proteinase did not evidence proteolytic processing or activation of proMMP-1, -8, and -9 under these experimental conditions. These results indicate that bacterial proteinases may play an important role in tissue destruction and disintegration of extracellular matrix at the site of infections.

The immunohistochemical localization of stat-2, -3, -4 and -5 during early enamel and dentine formation in rat molars

STATs (signal transduction and activators of transcription) are key components of the signal transduction pathways in the cytokine receptor superfamily-linked pathway. STATs are activated directly by members of the Jak (Janus kinase) family and, when activated, migrate to the nucleus to modify gene expression to produce a variety of cellular responses. Individual cytokines activate specific combinations of the Jak/STAT isoforms. A previous study localized the known Jak isoforms and STAT-1 in 5-day-old rat molars during the early stages of enamel and dentine formation. The present study was undertaken to localize immunohistochemically STAT isoforms STAT-2. -3, -4 and -5 in association with events involved in early dentine and enamel formation in 5-day-old rat molars. Each of the isoform localization patterns was different from the others. Combining the results of the previous study with the present findings, it appears that all of the known Jaks and STATs-1, -2, -3, -4 and -5 are located in the cells directly involved in early enamel or dentine formation. Using colocalization patterns of the individual Jaks and STATs, individual receptor locations may be predicted. In the proximal ends of differentiated ameloblasts, several cytokine receptors [interleukin (IL) -5, -6, -7, -9, -10, -12, growth hormone granulocyte colony-stimulating factor interferon-alpha/beta. -gamma] are predicted. In other areas of the early odontogenic cells, the proximal ends of differentiating ameloblasts are predicted to have IL-7 receptors, inner enamel epithelium IL-6 and IL-10 receptors, and stratum intermedium cells IL-6 receptors. In the early developing dentine, differentiating odontoblasts are predicted to have IL-6 and IL-10 receptors, and differentiated odontoblasts no cytokine receptors identified by known Jak/STAT combinations. Mapping of the Jak and STAT isoforms in the cells involved in early enamel and dentine formation indicates that a sizeable list of ligands and their respective cytokine receptor/pathway complexes are involved in the regulation of these processes.

The immunohistochemical localization of signal-transduction pathway components Jak1, Jak2, Jak3, Tyk2 and STAT-1 during early enamel and dentine formation in rat molars

This study sought to localize immunohistochemically Janus kinase (Jak) and Tyk isoforms and STAT-1 in association with events involved in early dentine and enamel formation in the rat molar. The Jaks and STATs (signal transducers and activators of transcription) are key signal-transduction pathway components in the cytokine receptor-linked pathway. The histological sections were not demineralized or fixed, providing optimum conditions for immunohistochemical localization. It appears that all of the Jak isoforms and STAT-1 are involved in enamel formation. Jak2 and STAT-1 colocalized in the proximal ends of presecretory and secretory-stage ameloblasts, supporting work by others that growth hormone receptor is located at that site. The colocalization of Jak1, Jak2 and STAT-1 along the proximal ends of presecretory and secretory ameloblasts suggests that the interferon receptor is up-regulated in these cells as well. Also, colocalization of Jak3 and STAT-1 in the proximal ends of the ameloblasts and the cells of the stratum intermedium predicts the location of the interleukin-7 receptor in those locations. Jak1, Tyk2 and STAT-1, but not Jak2 or Jak3, stain was seen in the odontoblasts.

Transient expression of collagen type XIV during muscle development and its reappearance after denervation and degeneration

In the formation of muscle pattern, the architectural arrangement is believed to be controlled by the local connective tissue cells. In this study we examined the immunohistological localization of Type XIV collagen recognized by a monoclonal antibody, MAb DBM, in embryonic chick hind limbs from stage (St.) 27 to 2 weeks post hatching. DBM staining was transiently observed in the epimysium from St. 30, in the perimysium of the dorsal region from St. 37, and in the entire perimysium from St. 39. After hatching, DBM staining was notably diminished in both epimysium and perimysium. In contrast, DBM staining and in situ hybridization signals for Type XIV collagen mRNA increased in the muscle connective tissues after denervation and around the regenerating muscle fibers. Therefore, Type XIV collagen expression appears to coincide with muscle activity and muscle regenerating conditions, and Type XIV collagen is considered to play roles in muscle development and regeneration.

The terminal protein of the linear DNA plasmid pGKL2 shares an N-terminal domain of the plasmid-encoded DNA polymerase

The 36K protein attached at the 5' end of the linear DNA plasmid pGKL2 from the yeast Kluyveromyces lactis was first purified and characterized. The terminal protein was purified from cells (1 kg wet weight) by ammonium sulphate precipitation and two rounds of centrifugation to equilibrium in CsCl gradients. The pGKL2 was present only in the post-microsomal supernatant. Approximately 10 mg of the purified pGKL2 was recovered and digested with DNase I. The terminal protein (final ca. 0 center dot 8 mg) was homogeneous by electrophoresis and we determined the N-terminal amino acid sequence up to ten residues, showing that it existed in the cryptic N-terminal domain of pGKL2-ORF2 (DNA polymerase) sequence.

Monocyte chemotactic factor in rheumatoid arthritis synovial tissue. Probably a cross-linked derivative of S19 ribosomal protein

The extracts of rheumatoid arthritis-synovial lesions from seven patients possessed a strong chemotactic activity for monocytes and a negligible one for polymorphonuclear leukocytes. These results are consistent with a prominent histological feature of the synovial lesion, the mononuclear cell predominant infiltration. The major monocyte chemotactic factor in the synovial tissue extracts was purified to a single protein peak in reverse phase high performance liquid chromatography with a C4 column. NH2-terminal amino acid analysis of the initial 20 residues yielded a single sequence. Surprisingly, this sequence was completely identical to that of S19 ribosomal protein. The purified sample demonstrated two protein bands in SDS-polyacrylamide gel electrophoresis with apparent molecular masses of 34 and 68 kDa. These sizes were 2 and 4 times that of S19 ribosomal protein, suggesting that the chemotactic factor would be a dimer or tetramer of S19 ribosomal protein cross-linked by factor XIIIa. A recombinant human S19 ribosomal protein was prepared as a fusion protein with a maltose binding protein in Escherichia coli. After treatment with factor XIIIa, cross-linked recombinant S19 ribosomal protein exhibited the monocyte chemotactic activity, although the untreated recombinant protein did not.

NMR studies of 1H resonances in the 10-18-ppm range for cytosolic aspartate aminotransferase

Continuing a previous investigation (Kintanar, A., Metzler, C. M., Metzler, D. E., and Scott, R. D. (1991) J. Biol. Chem. 266, 17222-17229), we have recorded 1H NMR spectra at 500 MHz in the 10-18-ppm range for the 93-kDa porcine cytosolic aspartate aminotransferase and for four specific mutant forms of the enzyme in which histidine 68 has been replaced by lysine or histidine 143, 189, or 193 has been replaced by glutamine. We have correlated resonances for apoenzyme, pyridoxamine and pyridoxal phosphate forms, and dicarboxylate complexes and have assigned imidazole NH resonances of active site histidines. The chemical shifts of several resonances undergo pH-dependent changes around the pKa of the Schiff base proton at the active site. Other resonances shift upon binding of dicarboxylates or other ligands. Phosphate or carboxylate ions, which can also occupy the site of the substrate's alpha-carboxylate, cause rapid exchange of the Schiff base proton. Although most resonances in the 10-18-ppm range disappear rapidly in D2O, a few are retained for months in the presence of the dicarboxylate inhibitor glutarate. We demonstrate that changes in chemical shifts and in exchange rates are sensitive indicators of electronic interactions of the enzyme with ligands and of conformational change. Nuclear Overhauser effects from NH protons have allowed us to identify resonances of CH protons of the imidazole rings of histidines 143, 189, and 193. Observed and predicted chemical shifts have been compared. We conclude that the net charge on this histidine cluster is zero but that some negative charge from the aspartate 222 carboxylate is donated inductively into the histidine 143 ring. Studies of the related enzyme from Escherichia coli are provided in an accompanying paper (Metzler, D. E., Metzler, C. M., Scott, R. D., Mollova, E. T., Kagamiyama, H., Yano, T., Kuramitsu, S., Hayashi, H., Hirotsu, K., and Miyahara, I. (1994) J. Biol. Chem. 269, 28027-28033). Our approach should be applicable to the study of active sites of a broad range of relatively large proteins.

Functional role of the amino-terminal mobile segment in catalysis by porcine cytosolic aspartate aminotransferase. Critical importance of Val17 and Phe18 for productive binding of substrates

A notable feature of porcine cytosolic aspartate aminotransferase is the closure of the active site cleft by a mobile amino-terminal segment (residues 15-40) upon binding substrate. The functional roles of Val17 and Phe18, residues that are part of the mobile loop, have been studied in the site-directed mutants in which the size and hydrophobic nature of these residues have been changed. Absorption, circular dichroism spectra, susceptibility to protease 401, and thermal stability did not differ appreciably between wild type and mutant enzymes. In the overall transamination between aspartate and 2-oxoglutarate, V17A represented a typical Km mutant while V17I retained the substrate binding affinity fairly well. In contrast, replacement of Phe18 by Ala resulted in a large decrease in both catalytic rate and binding affinity for substrates. F18W, F18Y, and F18H showed a moderate decrease in kcat and a considerable increase in Km values. Single-turnover reactions with four individual substrates yielded analogous results to those obtained for the overall reaction and, in addition, revealed that k/Kd values of mutants F18A and F18H were over 10 times lower for C5 substrates (glutamate and 2-oxoglutarate) than those for C4 substrates (aspartate and oxalacetate). All mutant enzymes showed variously increased Kd values for substrate analogs such as 2-methylaspartate, succinate, and glutarate. 1H NMR observations of F18H, in which His18 served as a built-in probe, were in accord with the behavior that would be expected from the conformational transition. We conclude that, although Val17 and Phe18 may not be essential for catalysis, the presence of a bulky residue of appropriate size at each position is critical for productive binding of substrate.

Ethylene production by strains of the plant-pathogenic bacterium Pseudomonas syringae depends upon the presence of indigenous plasmids carrying homologous genes for the ethylene-forming enzyme

The molecular characteristics of the ethylene-forming enzymes of strains of Pseudomonas syringae were tested. The ethylene-producing activities of the nine strains as measured in vivo and in vitro were similar, except for that of P. syringae pv. mori M5. A polyclonal antibody and a DNA probe for the ethylene-forming enzyme from P. syringae pv. phaseolicola PK2 were prepared to investigate homologies among the proteins and genes for the ethylene-forming enzymes. With the exception of P. syringae pv. mori M5, eight strains tested expressed the same antigen as the ethylene-forming enzyme from P. syringae pv. phaseolicola PK2 and were homologous to DNA sequences on indigenous plasmids. Molecular masses of antigenic proteins from all ethylene-producing strains were 40 kDa. The N-terminal amino acid sequence of the purified ethylene-forming enzyme from P. syringae pv. glycinea KN130 was identical to that of the enzyme from P. syringae pv. phaseolicola PK2. These results show that the ethylene-forming enzymes encoded by the indigenous plasmid(s) in the pathogenic bacteria examined were similar.

A novel nuclear protein with zinc fingers down-regulated during early mammalian cell differentiation

We introduced a promoter trap vector carrying a neo gene as a selectable marker into F9 cells and established several cell lines in which the expression of neo gene is under the control of an endogenous host gene that is active only in the undifferentiated F9 cells. Using one of these cell lines, G19, we isolated the integrated neo construct and its flanking host sequences by the plasmid rescue method, identified the host gene which contributes to the expression of neo gene, and named it the Zfp-57 gene. Two different Zfp-57 transcripts (1.8 and 3.2 kilobases) were identified in the undifferentiated F9 cells, and the levels of these transcripts were decreased significantly within a short time after induction of differentiation. We examined mouse organs for the presence of the Zfp-57 RNAs and found that the 1.8-kilobase RNA was detected only in the testis. The Zfp-57 cDNAs corresponding to the two different RNAs were isolated, and a comparison of the nucleotide sequences revealed that their coding regions were completely identical, but they differed both in length and in sequence of the 3'-untranslated region. The Zfp-57 cDNA encoded a protein consisting of 421 amino acids with an extremely high content of basic amino acid residues and multiple zinc finger motifs. Immunocytochemical analysis revealed that this protein is localized in the nucleus. These findings suggest that the Zfp-57 protein is a DNA-binding protein.

Familial carpal tunnel syndrome due to amyloidogenic transthyretin His 114 variant

We studied two patients from a Japanese family with carpal tunnel syndrome (CTS). The biopsy samples obtained during CTS surgical release revealed deposits of amyloid that stained with antihuman transthyretin (TTR) antiserum. Single-strand conformation polymorphism analysis and sequence analysis of polymerase chain reaction (PCR)-amplified exons of the proband's TTR gene revealed a point mutation resulting in a substitution of histidine for tyrosine at position 114. The mutation was confirmed by PCR-primer-induced restriction analysis. Our findings account for clinical heterogeneity of TTR-derived amyloidosis, and suggest the importance of substitution itself for deposits of amyloid in CTS.

Functional roles of valine 37 and glycine 38 in the mobile loop of porcine cytosolic aspartate aminotransferase

The functional roles of Val37 and Gly38 in porcine cytosolic aspartate aminotransferase have been studied in the site-directed mutants V37A, G38A, and G38S where the size and hydrophobic character of these residues has been altered. Previous x-ray studies have shown that Val37 and Gly38, which are part of a flexible loop, interact directly with bound substrate. From x-ray and solution experiments we find that the V37A, G38A, and G38S mutations do not cause significant perturbations to the unliganded enzyme. Replacing Val37 with a less bulky alanine residue does not affect the maximal catalytic rate (kcat), but it does increase significantly the Michaelis constants for substrates in the overall transamination reaction between aspartate and 2-oxoglutarate. On the other hand, replacing Gly38 with alanine or serine results in striking decreases in kcat to 5 and 0.6%, respectively, of the value observed for the wild-type enzyme, as well as in considerable increases in Km values. Consequently, the catalytic competence, kcat/Km, decreases by 3 orders of magnitude for G38A and by 4 orders of magnitude for G38S. Single turnover reactions of G38A and G38S with four individual substrates (aspartate, glutamate, oxalacetate, and 2-oxoglutarate) are characterized by kinetic parameters that are largely consistent with those of the overall reaction. In addition, the mutations at position 38 impair more seriously the catalytic competence of the enzyme toward C5-substrates than toward C4-substrates. We conclude that Gly38 is probably required for proper function of the enzyme because it permits a high level of flexibility for the 36-39 peptide, which in turn allows the essential substrate-induced movement of the small domain.

Purification and characterization of cytochrome P450 from an isobutene-forming microorganism, Rhodotorula minuta

A cytochrome P450 was purified from microsomes of Rhodotorula minuta. The optical spectrum of the purified cytochrome was characteristic of a low-spin ferric heme protein. Isovalerate caused a type I spectral change in it. The amino-terminal sequence of the cytochrome was different from those of other known microsomal cytochrome P450s. These results indicate that the cytochrome, which is tentatively named P450rm, is a novel species of cytochrome P450.

Thrombin generates monocyte chemotactic activity from complement factor H

We have recently found that the complement factor H (H) was the precursor of the major macrophage chemotactic factor in the delayed-type hypersensitivity (DTH) reaction site in the skin and was converted to the factor by an unidentified trypsin-like protease in plasma. Thrombin and plasmin are also present in the site, and we, therefore, examined the possibility that these proteases converted H to be monocyte chemotactic. Intact H caused no monocyte migration, although it was able to do so after incubation with thrombin, but not with plasmin. The activity was chemotactic rather than chemokinetic and was absorbed by an anti-H IgG-conjugated column. The generation of monocyte chemotactic activity from H was dependent on incubation time with thrombin and also the protease activity of thrombin, and the activity was seen at concentrations of H lower than 10(-8) M. The inhibitory activity of H for C3b-Bb was not affected by incubation with thrombin or plasmin. Incubation of H with thrombin, but not with plasmin, generated a hydrophobic molecule, in a time-dependent manner, which had monocyte chemotactic activity. These results show that H becomes a monocyte chemotactic factor due to cleavage by thrombin, which converts H to a more hydrophobic molecule and also suggest that thrombin-treated H induces monocyte migration in the DTH reaction site.

Novel function of C4a anaphylatoxin. Release from monocytes of protein which inhibits monocyte chemotaxis

The complement C4-derived anaphylatoxin, C4a, possesses a strong chemotaxis inhibitory capacity to blood monocytes at concentrations as low as 10(-16) mol/L. In our study, treatment with carboxypeptidase B to convert it to C4a des Arg77 decreased the inhibitory activity to less than 1/1,000. The extraordinary inhibitory capacity of C4a suggests the presence of an amplification mechanism in this inhibition. Indeed, we found that the conditioned media of peripheral blood mononuclear cells or monocyte/macrophage lineage cell lines (U937 and THP-1 cells) preincubated with 10(-16) mol/L C4a for 5 minutes or more at 37 C possessed the inhibitory capacity 100,000-fold stronger than the original activity of C4a. The monocyte-derived chemotaxis inhibitory factor seemed monocyte-specific. This cell-derived factor was sensitive to treatment with trypsin and chymotrypsin and immunologically distinct from C4a. The apparent molecular size of the monocyte factor was estimated to be approximately 20 kd by gel filtration. These results indicate that C4a anaphylatoxin induces the release from monocytes of a protein with inhibitory activity for monocyte chemotaxis.

Difference between human and guinea pig Hageman factors in activation by bacterial proteinases: cleavage site shift due to local amino acid substitutions may determine the activation efficiency of serine proteinase zymogens

Human and guinea pig Hageman factors have been subjected to the action of pseudomonal elastase and serratial E15 proteinase. The pseudomonal elastase cleaved 22-24% of the human molecule at Arg353-Val354, and the remainder at Gly357-Leu358 resulting in the generation of about 20% of potential activity as activated Hageman factor, compared with trypsin activation, while it hydrolyzed Arg340-Ile341 bond in guinea pig molecule and generated about 75% of activity as activated Hageman factor. The serratial proteinase did not hydrolyze the essential cleavage site (Arg353-Val354) of the human zymogen but Gly356-Gly357 (30%) and Gly357-Leu358 (70%) bonds. Both products showed no activity. The guinea pig zymogen, in contrast, was cleaved mostly at Arg340-Ile341 (70%) and less abundantly at Gly344-Leu345 (30%), generating about 85% of the whole potential activity as activated Hageman factor. From the high correspondence between the proportions of activation and of hydrolysis at the essential cleavage site in activation, it was concluded that hydrolysis of the bonds different from the essential bond did not cause activation, even when the spatial separation was only 3 or 4 residues. Considering the amino acid differences between human and guinea pig Hageman factors, -Met351-Thr-Arg-Val-Val-Gly-Gly-Leu-Val-Ala360- and -Leu338-Ser-Arg-Ile-Val-Gly-Gly-Leu-Val-Ala347-, respectively, it was realized that even the minor amino acid substitutions caused the cleavage site shift which resulted in significant differences in activation efficiency of the proteinase zymogens.

Two reactions are simultaneously catalyzed by a single enzyme: the arginine-dependent simultaneous formation of two products, ethylene and succinate, from 2-oxoglutarate by an enzyme from Pseudomonas syringae

A single enzyme isolated from Pseudomonas syringae pv. phaseolicola PK2 simultaneously catalyzed two reactions, namely, the formation of ethylene and succinate from 2-oxoglutarate, at a molar ratio of 2:1. In the main reaction, 2-oxoglutarate was dioxygenated to produce one molecule of ethylene and three molecules of carbon dioxide. In the sub-reaction, both 2-oxoglutarate and L-arginine were mono-oxygenated to yield succinate plus carbon dioxide and L-hydroxyarginine, respectively, the latter being further transformed to guanidine and L-delta 1-pyrroline-5-carboxylate. We propose a dual-circuit mechanism for the entire reaction, in which the binding of L-arginine and 2-oxoglutarate in a Schiff-base structure generates a common intermediate for two reactions.

Molecular cloning in Escherichia coli, expression, and nucleotide sequence of the gene for the ethylene-forming enzyme of Pseudomonas syringae pv. phaseolicola PK2

The gene for the ethylene-forming enzyme of Pseudomonas syringae pv. phaseolicola PK2 was found to be encoded by an indigenous plasmid, designated pPSP1. The gene for the ethylene-forming enzyme was cloned and expressed in Escherichia coli JM109. Nucleotide sequence analysis of the clone revealed an open reading frame that encodes 350 amino acids (mol. wt. 39,444). In a comparison with other proteins, the homology score for the entire amino-acid sequence of the ethylene-forming enzyme of Pseudomonas syringae versus ethylene-forming enzymes from plants and 2-oxoglutarate-dependent dioxygenases was low. However, functionally significant regions are conserved.

Primary structure of guinea-pig Hageman factor: sequence around the cleavage site differs from the human molecule

The guinea-pig and human Hageman factors differ in their sensitivity to activation by particular bacterial proteinases. To understand this difference, the primary structure and cleavage site on activation of the guinea-pig molecule were determined and compared with the human molecule. By the use of a synthetic oligodeoxyribonucleotide probe which encoded a part of human Hageman factor cDNA, a cDNA clone was isolated from a lambda gt11 cDNA library of guinea-pig liver and sequenced. The cDNA clone was identified as that of guinea-pig Hageman factor by the complete identity of the deduced amino-acid sequence with the actual sequence of the amino-terminal portion of guinea-pig Hageman factor molecule and the active form. The cDNA included part of a leader sequence and the entire coding region of the Hageman factor molecule. Guinea-pig Hageman factor was composed of the same domain structures as the human counterpart with an overall 72% homology in the amino-acid sequence. However, the sequences around the cleavage site were surprisingly different; -Met351-Thr-Arg-Val-Val-Gly-Gly-Leu-Val359-(human) and -Leu338-Ser-Arg-Ile-Val-Gly-Gly-Leu-Val346-(guinea-pig). The amino-acid substitutions around the cleavage site might explain the difference in sensitivity to activation between the human and guinea-pig molecules.

A novel transthyretin mutation at position 30 (Leu for Val) associated with familial amyloidotic polyneuropathy

A novel transthyretin (TTR) mutation associated with familial amyloidotic polyneuropathy was detected in a Japanese patient. Single-strand conformation polymorphism analysis and sequence analysis of polymerase chain reaction (PCR)-amplified exons of the patient's TTR gene revealed a point mutation resulting in a substitution of leucine for valine at position 30. As the mutation creates a Cfr13I site, it was confirmed by PCR and restriction analysis. Our finding indicates the importance of position 30 in TTR-derived amyloid fibril formation.

Presequence binding factor-dependent and -independent import of proteins into mitochondria

A cytosolic protein factor(s) is involved in the import of precursor proteins into mitochondria. PBF (presequence binding factor) is a protein factor which binds to the precursor form (pOTC) of rat ornithine carbamoyltransferase (OTC) but not to the mature OTC, and is required for the mitochondrial import of pOTC. The precursors for aspartate aminotransferase and malate dehydrogenase as well as pOTC synthesized in a reticulocyte lysate were efficiently imported into the mitochondria. However, the precursors synthesized in the lysate depleted for PBF by treatment with pOTC-Sepharose were not imported. Readdition of the purified PBF to the depleted lysate fully restored the import. pOTC synthesized in the untreated lysate sedimented as a complex with a broad peak of around 9 S, whereas pOTC synthesized in the PBF-depleted lysate sedimented at an expected position of monomer (2.5 S). When the purified PBF was readded to the depleted lysate, pOTC sedimented as a complex of about 7 S. In contrast to most mitochondrial proteins, rat 3-oxoacyl-CoA thiolase is synthesized with no cleavable presequence and an NH2-terminal portion of the mature protein functions as a mitochondrial import signal. The thiolase synthesized in the PBF-depleted lysate could be efficiently imported into the mitochondria, and readdition of PBF had little effect on the import. The thiolase synthesized in the untreated, the PBF-depleted, or the PBF-readded lysate sedimented at an expected position of monomer (2.5 S). These observations provide support for the existence of PBF-dependent and -independent pathways of mitochondrial protein import.

[Vitamin B6 dependency syndrome]

Many enzymes that require pyridoxal 5'-phosphate (PLP), a coenzyme from a vitamin B6, are involved in amino acid metabolism. B6 dependency syndromes are defined as a group of metabolic disorders which are prevented or alleviated by non-physiologically large doses of vitamin B6, and, hence, they are tacitly accounted for by some structural alteration in a responsible B6-dependent enzyme such as a decrease on the affinity for PLP as compared to the normal. In this article, the mode of binding the coenzyme is exemplified by the case of aspartate aminotransferase, a typical B6-dependent enzyme whose three-dimensional structure is known, and, several B6 dependency syndromes are briefly reviewed. Among these syndromes, the molecular basis of only gyrate atrophy has recently been defined by the identification of a mutation in the relevant enzyme, ornithine aminotransferase.