Interaction of GroEL with conformational states of horse cytochrome c

GroEL interacts with proteins in denatured states and promotes their efficient folding. To understand the conformational features required for the substrate, we studied the interactions of GroEL with various derivatives of horse cytochrome c including porphyrin-cytochrome c, apo-cytochrome c, and the three fragments containing the heme group, i.e. fragments 1-65, 1-38 and 11-21. Size-exclusion chromatography was performed, taking advantage of the heme absorption of the fluorescence label. Under low-salt conditions, significant binding to GroEL was observed for porphyrin-cytochrome c, apo-cytochrome c, and fragments 1-65 and 1-38, but not for intact cytochrome c or fragment 11-21. On the other hand, under conditions of high ionic strength, only apo-cytochrome c remained tightly bound. Whereas porphyrin-cytochrome c assumes a molten-globule-like compact conformation with a native-like far-UV CD, apo-cytochrome c shows a compact conformation without an ordered secondary structure. The far-UV CD spectra of the three fragments indicated that the fragments lack an ordered secondary structure. These results suggest that the fluctuating and exposed hydrophobic clusters of the substrates are responsible for the interaction, and that the interaction is modulated by electrostatic interaction. It is notable that these characteristics are similar to those of the interaction of cytochrome c derivatives with negatively charged phospholipid membranes, suggesting a common mechanism. Using fluorescence-labeled apo-cytochrome c, we also measured the kinetics of the interaction and estimated the association rate constant to be 5 x 10(7) M-1s-1. This relatively fast association rate constant indicates that the refolding rate of substrate protein is another important factor determining the interaction.

Expression of plasminogen activator inhibitor 2 in the adult and embryonic mouse tissues

We have studied the expression of plasminogen activator inhibitor 2 (PAI-2) in the adult mouse and during embryonic development using immunohistochemistry and the polymerase-chain reaction. Mouse PAI-2 mRNA was mainly expressed in the skin, bone-marrow, spleen, lung, thymus, and urinary bladder. Immunohistochemical studies suggested that PAI-2 was synthesized in macrophages and epithelial cells such as skin epithelial cells, transitional cells of the urinary bladder, and mesothelial cell of peritoneum and pleura. PAI-2 mRNA and antigen expression was observed only in the skin of 15 day-old mouse embryos. These data suggest that PAI-2 may play a role in protecting the mouse embryo from the protease attack in the amniotic fluid and also in maintaining and/or protecting the structure of various surfaces in the mouse.

[Molecular approach to detection of micrometastatic prostatic cancer cells in the lymph nodes and the bone marrow]

We detected micrometastatic prostate cancer cells in lymph nodes and bone marrow using reverse transcriptase-polymerase chain reaction (RT-PCT) specific for prostate-specific antigen (PSA). RT-PCR revealed PSA mRNA in two lymph nodes obtained from two patients with negative histological and immunohistochemical analyses for lymph node metastases. Of 26 patients with negative bone scan imaging, 7 had PSA mRNA detected in the bone marrow by RT-PCR. The RT-PCR will be a relevant tool to allow a more accurate clinical assessment of lymph node and bone metastases in patients with prostate cancer.

4Pi confocal optical system with phase conjugation

We propose a 4Pi confocal system that incorporates a phase-conjugate mirror into the system to solve the alignment problem and automatically correct the spherical aberration associated with the conventional 4Pi confocal system when observing a thick sample. The proposed system is experimentally verified by use of cerium-doped barium titanate crystal as the phase-conjugate mirror. The full width of the central peak is ~0.15 microm. We also theoretically verify the advantage of automatic correction of the spherical aberration by calculating the intensity distribution at the focal spot.

Randomly accessible, multilayered optical memory with a Bi(12)SiO(20) crystal

A read-and-write, randomly accessible, multilayered optical memory with a Bi(12) SiO(20) crystal as the medium is demonstrated. Data are recorded in the crystal as an absorption change that is due to the photochromic effect. These data are successfully recorded, read, and selectively erased in five layers in the crystal. The axial-separation distance between neighboring layers is 30 μm, and the lateral distance between bits is 5 μm. Selective bit erasure of the data is accomplished by illumination of the recorded bit datum with He-Ne laser light. To our knowledge, this is the first successful demonstration of the selective optical erasure of the photochromic effect in a BSO crystal.

An MRI analysis of brain-stem and cerebellar lesions and olivary hypertrophy

We describe the relations between primary brain stem or cerebellar infarct or haemorrhage and secondary inferior olivary pseudo-hypertrophy (OPH). We identified 17 patients (43.6%) among 39 with brain stem or cerebellar vascular disease who had MRI follow-up more than 3 months after their ictus, with OPH. The primary lesions in the 22 cases without OPH were 11 haemorrhages, including 8 medial cerebellar and 3 brain stem lesions, and 11 infarcts: 4 brain stem lesions without accompanying cerebellar involvement, 2 cerebellar infarcts with brain stem extension, and 5 cerebellar lesions without a brain stem infarct. The causative lesion in the 17 patients with OPH included 5 brain stem and 7 cerebellar haemorrhages and 5 brain stem infarcts; no cerebellar infarcts without brain stem involvement were found to cause OPH. Primary involvement of the tegmentum of the brain stem was closely related to secondary OPH, but we could not characterise MRI differences in the cerebellar lesions between the patients with or without OPH.

Readout of three-dimensional optical memories

The method of recording data in a volume memory determines the spatial frequency content. We use a threedimensional transfer function approach to show that this has serious implications for the choice of readout system. In particular, one cannot use a ref lection confocal system to read a photopolymer-based memory. A solution to this problem is proposed.

A gamma Gly-268 to Glu substitution is responsible for impaired fibrin assembly in a homozygous dysfibrinogen Kurashiki I

A new type of gamma Gly-268 (GGA) to Glu (GAA) substitution has been identified in a homozygous dysfibrinogen by analyses of the affected polypeptide and its encoding gene derived from a 58 year-old man manifesting no major bleeding or thrombosis. The functional abnormality was characterized by impaired fibrin assembly most likely due to failure to construct properly aligned double-stranded fibrin protofibrils. This presumption was deduced from the following findings: (1) Factor XIIIa-catalyzed cross-linking of the fibrin gamma-chains progressed in a normal fashion, indicating that the contact between the central E domain of one fibrin monomer and the D domain of another took place normally; (2) Nevertheless, factor XIIIa-catalyzed cross-linking of the fibrinogen gamma-chains was obviously delayed, suggesting that longitudinal association of D domains of different fibrin monomers, ie, D:D association was perturbed; (3) Plasminogen activation catalyzed by tissue-type plasminogen activator was not as efficiently facilitated by polymerizing fibrin monomer derived from the patient as by the normal counterpart. Therefore, gamma Gly-268 would not be involved in the 'a' site residing in the D domain, which functions as a complementary binding site with the thrombin-activated 'A' site in the central E domain, but would be rather involved in the D:D self association sites recently proposed for human fibrinogen. Thus, the gamma Glu-268 substitution newly identified in this homozygous dysfibrinogen seems to impair proper alignment of adjacent D domains of neighboring fibrin molecules in the double-stranded fibrin protofibril, resulting in delayed fibrin gel formation.

Three-dimensional optical bit-memory recording and reading with a photorefractive crystal: analysis and experiment

We analyze the three-dimensional refractive-index distribution that is induced locally when a laser beam is focused onto a very small region in a photorefractive crystal. The formation of the index distribution is deduced from the temporal behavior of the electron density distribution in the crystal under non-steady-state conditions. The density distribution is computed by the use of a set of the recurrence relations that was derived from Kukhtarev's equations, which describe the transport of electrons in time. In particular, we calculated the index distribution formed in Fe-doped LiNbO(3) crystals. To verify the validity of our analysis, we read, by using a phase-contrast microscope, refractive-index dots that were recorded in Fe-doped LiNbO(3) crystals. A good agreement was obtained between experimental results and the calculated phase-contrast images when the characteristics of the imaging system are taken into account. We also found that the induced index change is largest when the c axis of the LiNbO(3) crystal is oriented parallel to the polarization direction of the reading beam. Under this optimal condition, we succeeded in recording up to 10 layers of readable data in a LiNbO(3) crystal.

Differential phase-contrast microscope with a split detector for the readout system of a multilayered optical memory

A transmission differential phase-contrast microscope with a split detector is used as a readout system for a multilayered three-dimensional optical memory. The system is applicable to data recorded as refractive-index changes. The system is compact and easy to use. The three-dimensional optical transfer function for the system is derived. This shows that the spatial bandwidth of the system is the same as that of a conventional microscope with incoherent illumination but with much improved contrast. Six layers of information are recorded in a photopolymer and are read out with little cross talk and high contrast.

Prostaglandin E2 stimulates osteoclast formation via endogenous IL-1 beta expressed through protein kinase A

The present study was conducted to determine whether endogenous IL-1 is involved as a potent mediator of PGE2-stimulated osteoclast formation in 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25-(OH)2D3)-primed calvarial cells from mouse embryos. PGE2 induced IL-1 beta gene expression in the primed calvarial cells. IL-1 beta gene expression was also induced in a dose-dependent manner by forskolin and dibutyryl cAMP. PGE2-induced IL-1 beta gene expression was markedly inhibited by H-89, a potent inhibitor of protein kinase A. On the other hand, osteoclast formation in 1 alpha,25-(OH)2D3-primed calvarial cells was also stimulated by forskolin and dibutyryl cAMP, and their stimulatory effects were dose dependent. H-89 also inhibited PGE2-stimulated osteoclast formation. The presence of the IL-1 beta gene product in the conditioned medium of 1 alpha,25-(OH)2D3-primed calvarial cells treated with PGE2 was proved by the results of an immunoprecipitation assay using anti-mouse IL-1 beta Ab. The addition of anti-mouse IL-1 beta Ab to 1 alpha,25-(OH)2D3 primed calvarial cell cultures markedly inhibited PGE2-stimulated osteoclast formation. The stimulatory effect of conditioned medium of primed calvarial cells treated with PGE2 on osteoclast formation was also inhibited by anti-IL-1 beta Ab pretreatment. Furthermore, we found that endogenous IL-6 is partially involved in PGE2-stimulated osteoclast formation.

Prostaglandin E2 stimulates osteoclast formation via endogenous IL-1 beta expressed through protein kinase A

The present study was conducted to determine whether endogenous IL-1 is involved as a potent mediator of PGE2-stimulated osteoclast formation in 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25-(OH)2D3)-primed calvarial cells from mouse embryos. PGE2 induced IL-1 beta gene expression in the primed calvarial cells. IL-1 beta gene expression was also induced in a dose-dependent manner by forskolin and dibutyryl cAMP. PGE2-induced IL-1 beta gene expression was markedly inhibited by H-89, a potent inhibitor of protein kinase A. On the other hand, osteoclast formation in 1 alpha,25-(OH)2D3-primed calvarial cells was also stimulated by forskolin and dibutyryl cAMP, and their stimulatory effects were dose dependent. H-89 also inhibited PGE2-stimulated osteoclast formation. The presence of the IL-1 beta gene product in the conditioned medium of 1 alpha,25-(OH)2D3-primed calvarial cells treated with PGE2 was proved by the results of an immunoprecipitation assay using anti-mouse IL-1 beta Ab. The addition of anti-mouse IL-1 beta Ab to 1 alpha,25-(OH)2D3 primed calvarial cell cultures markedly inhibited PGE2-stimulated osteoclast formation. The stimulatory effect of conditioned medium of primed calvarial cells treated with PGE2 on osteoclast formation was also inhibited by anti-IL-1 beta Ab pretreatment. Furthermore, we found that endogenous IL-6 is partially involved in PGE2-stimulated osteoclast formation.

Heat-induced chaperone activity of HSP90

The 90-kDa stress protein, HSP90, is a major cytosolic protein ubiquitously distributed in all species. Using two substrate proteins, dihydrofolate reductase (DHFR) and firefly luciferase, we demonstrate here that HSP90 newly acquires a chaperone activity when incubated at temperatures higher than 46 degrees C, which is coupled with self-oligomerization of HSP90. While chemically denatured DHFR refolds spontaneously upon dilution from denaturant, oligomerized HSP90 bound DHFR during the process of refolding and prevented it from renaturation. DHFR was released from the complex with HSP90 by incubating with GroEL/ES complexes in an ATP-dependent manner and refolded into the native form. alpha-Casein inhibited the binding of DHFR to HSP90 and also chased DHFR from the complex with HSP90. These results suggest that HSP90 binds substrates to maintain them in a folding-competent structure. Furthermore, we found that HSP90 prevents luciferase from irreversible thermal denaturation and enables it to refold when postincubated with reticulocyte lysates. This heat-induced chaperone activity of HSP90 associated with its oligomerization may have a pivotal role in protection of cells from thermal damages.

Crystal structure of Streptomyces erythraeus trypsin at 1.9 A resolution

A trypsin-like serine protease from Streptomyces erythraeus (abbreviated as SET) has been crystallized at pH 7, which is within its active pH range. The crystal structure of SET has been solved by molecular replacement using the atomic model of Streptomyces griseus trypsin (SGT), which is 37% homologous with SET, and refined to the crystallographic R factor of 0.199 for 15,878 reflections with Fo/sigma(F) > 3 between 7 and 1.9 A resolution. The final model of SET contains 1,619 protein atoms and 97 water molecules. No Ca2+ ion is present in SET apparently because (i) the two carboxylate groups from two Glu residues, which bind a Ca2+ ion in bovine trypsin (BT) or SGT, have disappeared; and (ii) a guanidino group from an Arg residue is unfavorably present in the potential binding region. There is an unusual type II beta-turn in which the third residue is Asp instead of Gly. This Asp residue is the only non-Gly residue significantly outside the allowed regions in the Ramachandran map. The three-dimensional structure of SET is essentially the same as those of other trypsins of mammalian origin. The 211 C alpha atoms of SET exhibit an r.m.s. deviation of 1.16 A with equivalent atoms of BT, and the 208 equivalent C alpha atoms between SET and SGT exhibit an r.m.s. deviation of 1.09 A. The large deviations in C alpha positions between SET and BT or between SET and SGT are mainly observed in the first domain. The conformations of the side-chains of the catalytic triad are mutually similar to each other in these three proteases. Each of the chi 1 torsion angles of the three residues is distributed within +/- 5 degrees from each corresponding mean value. The hydrogen bond distances related to the side-chains in the triad coincide fairly well, though the relative disposition of the side-chains differs by 0.1-0.6 A among SET, BT, and SGT. The hydrogen bond network concerned with Ser(195), Asp(189), and water molecules in the substrate binding pocket differs from that in BT or SGT.

The role of ATP hydrolysis in the function of the chaperonin GroEL: dynamic complex formation with GroES

In order to understand the role of ATP hydrolysis of the chaperonin GroEL during protein folding, we have studied GroEL-GroES complex formation in the presence of ATP or ADP by using capillary electrophoresis and surface plasmon resonance. Capillary electrophoresis analysis showed that the GroEL 14-mer and GroES 7-mer formed a 1:1 complex in the presence of ATP. In the presence of ADP, both the association and dissociation rates of the complex were slower by about one order of magnitude than the rates in the presence of ATP at 25 degrees C. The implications of such a stable complex on the overall mechanism of chaperonin function are discussed.

Three-dimensional optical memory with a photorefractive crystal

We propose a three-dimensional optical-memory device in which refractive dot data are recorded directly into a photorefractive crystal. To record a single bit of datum, one focuses a laser beam with an objective lens onto a specific spot in a crystal, thereby changing its refractive index locally as a result of photorefraction. To record in three dimensions, one keeps the objective lens stationary while the crystal is translated. The beam-spot intensity is modulated with a beam shutter according to the logic state of the data point. The recorded data points are read with a phase-contrast microscope objective lens. We present experimental results of three-dimensional recording and reading with a LiNbO(3) crystal. The distribution of the refractive index formed by a focused beam is also analyzed with the charge-transport model.

Porphyromonas gingivalis fimbria-stimulated bone resorption in vitro is inhibited by a tyrosine kinase inhibitor

Our previous study (Y. Kawata, S. Hanazawa, S. Amano, Y. Murakami, T. Matsumoto, K. Nishida, and S. Kitano, Infect. Immun. 62:3012-3016, 1994) showed that Porphyromonas gingivalis fimbriae stimulate bone resorption in vitro. Since it has recently been demonstrated that tyrosine kinase encoded by the c-src gene plays an important role in osteoclastic bone resorption, in the present study we examined the effect of a tyrosine kinase inhibitor on the fimbria-stimulated bone resorption. Genistein, a potent inhibitor of tyrosine kinase, markedly inhibited bone resorption stimulated by the fimbriae. Genistein also inhibited induction of several tyrosine-phosphorylated proteins in the fimbria-treated calvarial bone cells from mouse embryos.

Stability of ribonuclease T2 from Aspergillus oryzae

The stability of ribonuclease T2 (RNase T2) from Aspergillus oryzae against guanidine hydrochloride and heat was studied by using CD and fluorescence. RNase T2 unfolded and refolded reversibly concomitant with activity, but the unfolding and refolding rates were very slow (order of hours). The free energy change for unfolding of RNase T2 in water was estimated to be 5.3 kcal.mol-1 at 25 degrees C by linear extrapolation method. From the thermal unfolding experiment in 20 mM sodium phosphate buffer at pH 7.5, the Tm and the enthalpy change of RNase T2 were found to be 55.3 degrees C and 119.1 kcal.mol-1, respectively. From these equilibrium and kinetic studies, it was found that the stability of RNAse T2 in the native state is predominantly due to the slow rate of unfolding.

In vivo effect of GroESL on the folding of glutamate racemase of Escherichia coli

The overexpression of the murI (glr) gene, which encodes the glutamate racemase of Escherichia coli, resulted in the formation of inclusion bodies of the enzyme, and little activity was found in the soluble fraction of the transformant cells. The coexpression of the groESL gene with murI caused an in vivo solubilization of glutamate racemase in an active form. We isolated the active enzyme and purified it effectively.

The folding characteristics of tryptophanase from Escherichia coli

The unfolding and refolding characteristics of Escherichia coli tryptophanase (tryptophan indole-lyase) [EC 4.1.99.1] in guanidine hydrochloride were studied. Tryptophanase unfolded by first dissociating its coenzyme, pyridoxal 5'-phosphate, from the active site. This dissociation caused a significant destabilization of structure, and global unfolding of the protein followed. During this global unfolding step, an intermediate was formed which had a strong tendency to aggregate irreversibly, as detected by light scattering experiments. Tryptophanase was unable to refold quantitatively after unfolding in 4 M guanidine hydrochloride. The low refolding yield was due to non-specific aggregation which occurs during refolding. Various conditions which limited this aggregation were probed, and it was found that by initiating the refolding reaction at low temperature, the aggregation of tryptophanase folding intermediates during the reaction could be avoided to a certain extent, and the refolding yield improved.

The guanidine-induced conformational changes of the chaperonin GroEL from Escherichia coli. Evidence for the existence of an unfolding intermediate state

Equilibrium unfolding experiments of the E. coli chaperonin GroEL were performed in guanidine hydrochloride. A reversible unfolding intermediate was observed in very low concentrations of denaturant (< 0.5 M guanidine hydrochloride). This intermediate was characterized by a decreased light scattering intensity and an increased binding of the fluorescent probe 1-anilino-8-naphthalene sulfonate. No significant changes in circular dichroism spectra were observed for this unfolding intermediate. A second decrease in fluorescence intensity and light scattering was observed in higher concentrations of guanidine hydrochloride, with a transitional midpoint of 1.15 M. This transition was accompanied by the complete loss of secondary structure, as monitored by circular dichroism spectroscopy. This second transition agreed well with the results previously reported in this journal (Price et al. (1993) Biochim. Biophys. Acta 1161, 52-58).

Porphyromonas gingivalis fimbriae stimulate bone resorption in vitro

Our previous study demonstrated that Porphyromonas gingivalis fimbriae induce the expression of interleukin-1, a potent bone-resorbing cytokine, in macrophages. This demonstration suggested to use the possibility that the fimbriae may stimulate bone resorption via the generation of an inflammatory cytokine(s). The present study was performed to test this suggestion. The bone-resorbing activity was evaluated by measuring the area of resorption lacunae on bone slices incubated with calvarial bone cells taken from 14-day-old mouse embryos. Fimbriae at 0.5 micrograms of protein per ml stimulated the bone-resorbing activity significantly, and the effect was dose and treatment time dependent. Since it is well known that interleukin-1 and granulocyte macrophage colony-stimulating factor induce differentiation of osteoclast lineage cells, we examined the involvement of these cytokines in fimbria-stimulated bone resorption. Fimbria-stimulated bone resorption was abolished significantly by antisera against both cytokines. We observed by Northern (RNA) blot assay that both cytokine genes were markedly expressed in the fimbria-treated calvarial bone cells. Our present data demonstrate that P. gingivalis fimbriae stimulate bone resorption in vitro.

Chaperonin GroE and ADP facilitate the folding of various proteins and protect against heat inactivation

In the presence of ADP, the molecular chaperones GroEL and GroES from Escherichia coli not only facilitated the refolding of various proteins, but also prevented their irreversible heat inactivation in vitro. Without nucleotides the refolding reactions were arrested by GroEL. Addition of GroES and ADP to the reaction mixture initiated the refolding reactions and the enzyme activities were regained efficiently. The presence of GroE (GroEL and GroES) and ADP also protected against heat inactivation of native enzymes at various temperatures. These findings suggest that in the presence of GroES, nucleotide binding is an important event in the mechanism of GroEL-facilitated protein folding.

Phorbol myristate acetate stimulates osteoclast formation in 1 alpha,25-dihydroxyvitamin D3-primed mouse embryonic calvarial cells by a prostaglandin-dependent mechanism

Our previous study provided a novel assay system utilizing devitalized bone slices for study of the differentiation of osteoclast progenitors into preosteoclasts and mature osteoclasts among calvarial cells of mouse embryos. Using this assay system, we examined the effect of phorbol myristate acetate (PMA) on osteoclast formation as assessed by the appearance of tartrate-resistant acid phosphatase (TRAP)-positive cells and bone resorption lacunae. PMA alone was directly unable to induce the appearance of TRAP-positive cells and bone resorption lacunae of calvarial bone cells of mouse embryos. However, PMA markedly stimulated increases in the number of TRAP-positive cells and area of the resorption lacunae of the calvarial cells when the bone cells were primed by 1 alpha,25-(OH)2D3. This stimulatory effect of PMA was dose dependent. H-7, having relatively high affinity for protein kinase C, strongly inhibited in a dose-dependent fashion the stimulatory effect of PMA on the bone resorption of the hormone-primed calvarial cells. We also examined the involvement of prostaglandin in this stimulatory effect of PMA. Indomethacin, a cyclooxygenase inhibitor, markedly abolished the stimulatory effect of PMA on the bone resorption of the calvarial cells. PMA stimulated prostaglandin E2 (PGE2) production by the calvarial cells primed with 1 alpha,25-(OH)2D3 in a dose-dependent fashion. However, the PMA stimulation of the PGE2 production was significantly inhibited by H-7 and also by indomethacin. Furthermore, we observed that the addition of PGE2 to the calvarial cells primed with 1 alpha,25-(OH)2D3 for 1 or 3 days resulted in an increased number of TRAP-positive cells and increased bone resorption.(ABSTRACT TRUNCATED AT 250 WORDS)

[Ossified epidural hematomas: report of two cases]

Two cases of ossified epidural hematomas were reported. Patients were nine and twelve year-old boys. Initially they were both followed up conservatively after injuries. Subsequently they were found on CT scan to have calcifications in the capsules of epidural hematomas which were found four months after injury in one case and twelve days after injury in the other. Both underwent craniotomy and histological ossification was found in the capsules of the hematomas. Epidural hematomas in children are known to ossify, and this condition may prevent natural absorption of epidural hematomas. Therefore, careful follow up of hematomas seems to be mandatory on conservative therapy of epidural hematomas in children.