Complete amino acid sequence of bovine colostrum low-Mr cysteine proteinase inhibitor

Utility of Serum Cystatin C as a Clinical Measure of Renal Function in Dogs

A human kit for cystatin C determination was evaluated for use with canine sera. A reference range was also established. The association between cystatin C and glomerular filtration rate (GFR) was evaluated in 60 dogs with various diseases, by using exogenous creatinine plasma clearance (ECPC) as a measure of GFR. The correlation between cystatin C and ECPC (correlation coefficient [r] = −0.630; P<0.001) was stronger than the correlation between serum creatinine and ECPC (r = −0.572; P<0.001). Nonrenal diseases (e.g., neoplasia, infection) did not influence serum cystatin C concentration. Test sensitivity was significantly better (P<0.001) for cystatin C (76%) than for creatinine (65%). Specificities for the two tests were 87% and 91%, respectively.

Truncated cystatin C in cerebrospiral fluid: Technical artefact or biological process?

Cystatin C, a low molecular weight cysteine proteinase inhibitor present in human body fluids at physiological concentrations, is more expressed in cerebrospinal fluid (CSF) than in plasma. Mass spectrometric characterization showed that after 3 months of storage of human CSF at -20 degrees C, cystatin C was cleaved in the peptide bond between R8 and L9 and lost its eight N-termini amino acids, whereas this cleavage did not occur when stored at -80 degrees C. This truncation occurred in all CSF samples studied irrespective of the underlying neurological status, indicating a storage-related artefact rather than a physiological or pathological processing of the protein. These results stress the importance of optimal preanalytical storage conditions of any sample prior to proteomics studies.

New functions of lactoferrin and beta-casein in mammalian milk as cysteine protease inhibitors

We found new inhibitory function of lactoferrin and beta-casein in milk against cysteine proteases using reverse zymography. The inhibition of cathepsin L by lactoferrin was strongest and the inhibition kinetics were of a non-competitive type. Heat denatured lactoferrin lost the inhibitory activity completely, therefore the tertiary structure is essential to show the inhibition. Native lactoferrin was not degraded by papain during the assay condition. The intramolecular peptide, Y(679)-K(695), of lactoferrin is an active domain and the synthesized peptide inhibited cysteine proteases. The Y(679)-K(695) peptide showed 90% homology with the sequences of a common active site of cystatin family. beta-Casein and the active domain, synthesized L(133)-Q(151), peptide inhibited cysteine proteases. Lactoferrin and beta-casein in milk might play a role in antiseptic and antiinfectious functions due to cysteine protease inhibition of bacteria and viruses.

Cystatin C in milk basic protein (MBP) and its inhibitory effect on bone resorption in vitro

A cystein protease inhibitor was identified in the basic fraction of bovine milk. We have reported in our previous study that the milk basic protein (MBP) fraction suppressed osteoclast-mediated bone resorption in vitro. Since osteoclasts secreted cystein protease to digest collagen in the bone matrix, we identified the cystein protease inhibitor in MBP. A 12-kDa inhibitor was purified from MBP by papain affinity gel chromatography and subsequent Hi-Load Superdex 75 gel filtration chromatography. The N-terminal sequence of the 18 amino acid residues of the inhibitor corresponded to bovine cystatin C. The 12-kDa cystein protease inhibitor in MBP therefore seemed to be cystatin C. Purified cystatin suppressed bone resorption with the use of isolated osteoclasts in vitro. Cystatin in MBP is suggested as one of the factors inhibiting bone resorption.

Secretion of whey acidic protein and cystatin is down regulated at mid-lactation in the red kangaroo (Macropus rufus)

Milk collected from the red kangaroo (Macropus rufus) between day 100 and 260 of lactation showed major changes in milk composition at around day 200 of lactation, the time at which the pouch young begins to temporarily exit the pouch and eat herbage. The carbohydrate content of milk declined abruptly at this time and although there was only a small increase in total protein content, SDS PAGE analysis of milk revealed asynchrony in the secretory pattern of individual proteins. The levels of alpha-lactalbumin, beta-lactoglobulin, serum albumin and transferrin remain unchanged during lactation. In contrast, the protease inhibitor cystatin, and the putative protease inhibitor whey acidic protein (WAP) first appeared in milk at elevated concentrations after approximately 150 days of lactation and then ceased to be secreted at approximately 200 days. In addition, a major whey protein, late lactation protein, was first detected in milk around the time whey acidic protein and cystatin cease to be secreted and was present at least until day 260 of lactation. The co-ordinated, but asynchronous secretion of putative protease inhibitors in milk may have several roles during lactation including tissue remodelling in the mammary gland and protecting specific proteins in milk required for physiological development of the dependent young.

The affinity and kinetics of inhibition of cysteine proteinases by intact recombinant bovine cystatin C

Recent studies have shown that the bovine cysteine proteinase inhibitor, cystatin C, is synthesized as a preprotein containing a 118-residue mature protein. However, the forms of the inhibitor isolated previously from bovine tissues had shorter N-terminal regions than expected from these results, and also lower affinity for proteinases than human cystatin C. In this work, we report the properties of recombinant, full-length bovine cystatin C having a complete N-terminal region. The general characteristics of this form of the inhibitor, as reflected by the isoelectric point, the far-ultraviolet circular dichroism spectrum, the thermal stability and the changes of tryptophan fluorescence on interaction with papain, resembled those of human cystatin C. The affinity and kinetics of inhibition of papain and cathepsins B, H and L by the bovine inhibitor were also comparable with those of the human inhibitor, although certain differences were apparent. Notably, the affinity of bovine cystatin C for cathepsin H was somewhat weaker than that of human cystatin C, and bovine cystatin C bound to cathepsin L with about a four-fold higher association rate constant than the human inhibitor. This rate constant is comparable with the highest values reported previously for cystatin-cysteine proteinase reactions. The full-length, recombinant bovine cystatin C bound appreciably more tightly to proteinases than the shorter form characterized previously. Digestion of the recombinant inhibitor with neutrophil elastase resulted in forms with truncated N-terminal regions and appreciably decreased affinity for papain, consistent with the forms of bovine cystatin C isolated previously having arisen by proteolytic cleavage of a mature, full-length inhibitor.

Inhibitory activity against plasmin, trypsin, and elastase in rennet whey and in cheese fortified with whey protein

The inhibitory activity against trypsin, elastase, and plasmin was determined in samples of Danbo 45+ that were manufactured from milk pasteurized at 72, 80, and 90 degrees C for 15, 30 and 60 s; the corresponding rennet wheys; and Havarti 45+ manufactured from milk concentrated 1.8-fold, 2.7-fold, and 4.6-fold by ultrafiltration. A sensitive colorimetric assay demonstrated that the incorporation of thermally denatured whey proteins into the cheese curd by pasteurization resulted in a decreased proteinase inhibitory activity against trypsin and elastase in Danbo 45+ and against trypsin, elastase, and plasmin in the corresponding rennet wheys. However, incorporation of native whey proteins into Havarti 45+ by ultrafiltration of the cheese milk resulted in an increased inhibitory activity against trypsin and elastase in the cheeses. Cheese manufactured from milk concentrated 1.8-fold, 2.7-fold, or 4.6-fold displayed trypsin inhibitory activity that was 1.8, 2.9, and 5.1 times, respectively, that of the reference cheese. Similarly, the elastase inhibitory activity in the cheeses increased 2.2, 3.2 and 7.8 times. The increased inhibitory activity in cheese fortified with native whey protein likely contributes to the decreased proteolysis and altered ripening characteristics of the resulting cheeses, and further, the method can be adapted to detection of other inhibitors if sufficiently sensitive substrates are available.

Molecular cloning and N-terminal analysis of bovine cystatin C. Identification of a full-length N-terminal region

The N-terminal region of human cystatin C has been shown to be of crucial importance for the interaction of the inhibitor with cysteine proteinases. However, several studies have been unable to identify the corresponding region in bovine cystatin C, indicating that the binding of proteinases to the bovine inhibitor may not be dependent on this region. With the aim to resolve this apparent discrepancy and to elucidate the relation of bovine cystatin C to other cystatins, we have isolated a cDNA clone encoding bovine precystatin C. The sequence of this cDNA was similar to that of the human inhibitor and showed a putative signal peptidase cleavage site consistent with the N-terminal regions of the bovine and human inhibitors being of comparable size. This suggestion was verified by determination of the relative molecular mass of the mature bovine inhibitor isolated from cerebrospinal fluid under conditions minimising proteolysis. The N-terminal of the purified inhibitor was blocked, but the sequence of the N-terminal peptide produced by digestion with endopeptidase LysC could be unequivocally determined by tandem mass spectroscopy. Together, these results show that bovine cystatin C has 118 residues, in contrast with 110-112 residues reported previously, and has an N-terminal region analogous to that of human cystatin C. This region presumably is of similar importance for tight binding of target proteinases as in the human inhibitor.

Interactions between ovine cathepsin L, cystatin C and alpha 2-macroglobulin. Potential role in the genital tract

The specific inhibitor of cysteine proteinases, cystatin C, was purified from ram rete testis fluid and the conditioned medium of Sertoli cells. This molecule associated with sheep liver cathepsin L at one of the fastest rates ever described for a proteinase/inhibitor interaction (1.75 +/- 0.20 x 10(8) M-1.s-1). But the association rate constant for the interaction of cathepsin L with alpha 2-macroglobulin, a non-specific inhibitor of proteinases, was also extremely high (8.8 +/- 0.75 x 10(6) M-1.s-1). Cathepsin L complexed with alpha 2-macroglobulin was protected from inhibition by type 2 and type 3 cystatins. The data indicate that cystatin C is the most potent inhibitor of cathepsin L in mammalian male genital tract fluids, whereas alpha 2-macroglobulin may act as a terminal acceptor of this enzyme. These inhibitors could therefore inhibit the activated form of procathepsin L which may appear during the complex process of spermatozoa production and maturation in the testis and epididymis.

Mouse and rat cystatin C: Escherichia coli production, characterization and tissue distribution

Recombinant mouse (Mus musculus) and rat (Rattus norvegicus) cystatin C were produced by expression in Escherichia coli, isolated and functionally characterized. The mouse and rat inhibitors were both fully active in titrations of papain. Determination of equilibrium constants for dissociation (Ki) for their complexes with the target proteinase, cathepsin B, produced values not largely different from that for human cystatin C (Ki 0.07-0.13 nM). Rabbit antisera against mouse and rat cystatin C were produced and used for improved affinity purification of the recombinant inhibitors. Affinity purified immunoglobulins isolated from the antiserum against mouse cystatin C were used for construction of a sensitive enzyme-linked immunosorbent assay. The assay was used to demonstrate a high degree of immunological cross-reactivity between mouse and rat cystatin C and could be used for cystatin C quantification in mouse and rat tissue homogenates. All tissues analyzed contained cystatin C, with a relative content very similar to that of human tissues. For all species, brain tissue contained the highest cystatin C amounts and liver the lowest, whereas kidney, spleen and muscle tissues were intermediate in content. In the mouse, a notable high cystatin C content in parotid gland tissue was observed. The high degree of similarity in distribution pattern and functional properties for mouse, rat and human cystatin C indicates that a murine model should be relevant for studies of the human disease, hereditary cystatin C amyloid angiopathy.

Molecular cloning and sequence analysis of a cDNA encoding a cysteine proteinase inhibitor from Sorghum bicolor seedlings

A 711-bp cDNA encoding a cysteine proteinase inhibitor (cystatin) was isolated from a cDNA library prepared from 7-10 cm Sorghum bicolor seedlings. The nearly full-length cDNA clone encodes 130 amino acid residues, which include the Gin-Val-Val-Ala-Gly motif, conserved among most of the known cystatins as a probable binding site for cysteine proteinases. The amino acid sequence of sorghum cystatin deduced from the cDNA clone shows significantly homology to those of other plant cystatins. The sorghum cystatin expressed in E. coli showed a strong papain-inhibitory activity.

Purification and molecular cloning of carp ovarian cystatin

The ovarian fluid of carp consists of many components. Using the antiserum against carp serum, Western blot analysis of ovarian fluid was done in order to distinguish substances synthesized by the ovary from those derived from the serum. Several ovary-specific substances were detected including a protein of 12 kDa (p12), which was purified to homogeneity. Purified p12 displays a single band in SDS-PAGE under nonreducing condition and it can inhibit the enzymatic activity of papain with an apparent inhibition constant of 0.01 nM. The primary structure of p12 was partially determined by Edman degradation and fully elucidated by molecular cloning. A cDNA of 531 bp encoding p12 was obtained. The precursor of p12 has 129 residues, including a signal peptide of 18 residues and a mature protein of 111 residues. The N- and C-terminus of p12 are threonine and methionine, respectively. The p12 shares many common features of the family 2 cystatins of other species, including the similarity of the protein size (in the range of 110 to 120 residues), the presence of 4 cysteine residues and the occurrence of invariant residues throughout the molecule.

Characterization of cystatin C from bovine parotid glands: cysteine proteinase inhibition and antiviral properties

Cystatin C, a low Mr cysteine proteinase inhibitor was isolated from bovine parotid glands by a procedure which includes alkaline treatment of the homogenate, affinity chromatography, gel filtration and ion exchange chromatography. The purified inhibitor has a pl of 8.0 and Mr of 14500. The identity with bovine cystatin C from colostrum was confirmed by N-terminal sequence of the inhibitor and amino acid composition. Cystatin C rapidly (kass = 5.5 x 10(7) M-1s-1) and tightly inhibits papain (Ki = 0.02 nM), whereas its interaction with bovine cathepsin B is substantially weaker (Ki = 4.4 nM). Bovine cystatin C also shows a weak antiviral effect on poliovirus infected human Hela cells.

Identification of bovine stefin A, a novel protein inhibitor of cysteine proteinases

For the first time, three different stefins, A, B and C, have been isolated from a single species. The complete amino acid sequence of bovine stefin A was determined. The inhibitor, with a calculated M(r) of 11,123, consists of 98 amino acid residues. Although it exhibits considerable similarity to human and rat stefin A, some significant differences in inhibition kinetics were found. Bovine stefin A bound tightly and rapidly to cathepsin L (kass = 9.6 x 10(6) M-1.s-1, Ki = 29 pM). The binding to cathepsin H was also rapid (kass = 2.1 x 10(6) M-1.s-1), but weaker (Ki = 0.4 nM) due to a higher dissociation rate constant. In contrast, the binding to cathepsin B was much slower (kass = 1.4 x 10(5) M-1.s-1), but still tight (Ki = 1.9 nM).

Inhibitory activities of partially degraded salivary cystatins

1. Aminoterminally truncated forms of cystatin S and cystatin SN had higher inhibition constants for ficin, but lower ones for cathepsin C (dipeptidyl peptidase I) as compared to their respective full-sized form. 2. Cystatin SN still retained the inhibitory activity for ficin after reduction and carboxymethylation, although the inhibition constant increased.

Purification and characterization of acute phase rat plasma thiostatin

Thiostatin was purified from acute phase plasma of turpentine-treated rats by a novel, single-step carboxymethyl-papain Sepharose 4B column chromatographic procedure. Purified thiostatin appeared as a single band in SDS-PAGE with an estimated molecular weight of 68,000. Western blot with polyclonal rabbit anti-thiostatin IgG confirmed a homogeneous immuno-reactive 68 kDa species. Specific activity, as determined by enzyme-linked immunosorbent assay (ELISA), was 0.972 mg kininogen equivalent per mg protein. The yield of thiostatin exceeded 60% and the protein was purified 10.7-fold.

Modulation of thrombin-induced platelet aggregation by inhibition of calpain by a synthetic peptide derived from the thiol-protease inhibitory sequence of kininogens and S-(3-nitro-2-pyridinesulfenyl)-cysteine

Thrombin-induced platelet aggregation has been suggested to play an important role in reocclusion following thrombolytic therapy of angioplasty for treatment of myocardial infarction. We previously demonstrated that aggregation of washed platelets by thrombin is accompanied by cleavage of aggregin, a putative ADP receptor, and that these events are indirectly mediated by calpain, expressed on the surface of the external membrane. High-molecular-mass kininogen (HK) contains, in its heavy chain, domain 2, which is responsible for its action as a potent inhibitor of platelet calpain. Domain 3 of the heavy chain of HK directly inhibits binding of thrombin to platelets, confounding mechanistic studies using the entire molecule. Moreover, HK, a protease of 120 kDa, is unsuitable as a potential pharmacological agent. The highly conserved sequence Gln-Val-Val-Ala-Gly, present in HK and its evolutionary precursors, the cystatins, is thought to be involved in the binding of cysteine proteases but is, itself, not inhibitory. An affinity analog, Phe-Gln-Val-Val-Cys(Npys)-Gly-NH2(Npys, 3-nitro-2-sulfenylpyridine), P1, corresponding to the thiol-protease-binding sequence in HK and containing a ligand, Npys, that can react with the free sulfhydryl group in the active site of calpain, was synthesized. P1 was an irreversible inhibitor of platelet calpain. P1 selectively inhibited thrombin-induced aggregation of washed platelets and platelets in plasma, but did not inhibit the aggregatory effects of other platelet agonists. P1 did not inhibit the amidolytic activity and coagulant activity of thrombin. Unlike HK, P1 did not inhibit binding of thrombin to washed platelets. P1 did not inhibit thrombin-induced platelet-shape change. P1 neither raised intracellular levels of cAMP nor did it interfere with the ability of thrombin to antagonize the rise in intracellular levels of cAMP induced by iloprost, an analog of prostaglandin I2. The design and synthesis of P1 could leave to the development of a new class of inhibitors that selectively block thrombin-induced platelet aggregation while sparing other functions of this pathophysiological protease and without inhibiting the action of other platelet agonists.

The complete primary structure of bovine stefin B

A new stefin B-type low-Mr CPI was isolated from bovine thymus and subjected to structural analysis. The inhibitor consisted of 98 amino acids and its Mr was calculated to be 11,178. The NH2-terminal amino acid residue was blocked. The sequence was determined by automated sequencing of peptides derived by cleavage with cyanogen bromide and fragments of the inhibitor resulting from enzymatic digestion with beta-trypsin and Staphylococcus aureus V-8 proteinase. The NH2-terminal blocking group was established with mass spectrometry. The inhibitor exhibits considerable sequence homology with inhibitors from the stefin family. Furthermore, a highly conserved QVVAG region within the stefin family is for the first time replaced by the QLVAG sequence.

Characterization of an Onchocerca volvulus cDNA clone encoding a genus specific antigen present in infective larvae and adult worms

The isolation and characterization of a recombinant cDNA clone (OV7) expressing an antigen present in Onchocerca volvulus infective larvae and adult stages is described. Using chimpanzee antiserum generated against irradiated infective larvae, we isolated a cDNA clone from a lambda gt11 cDNA expression library derived from adult O. volvulus mRNA. The open reading frame encodes 131 amino acids corresponding to a 15.2-kDa protein. Affinity purified antibodies which bound specifically to OV7 fusion polypeptide recognized a single antigen with an apparent molecular weight of 17,000 in extracts of L3, L4 and adult worms. Immunoelectron microscopy established that the antigen encoded by this clone is present in the hypodermis and the basal layer of the cuticle of L3 and female adult worm, and in the egg shell around developing microfilariae. Since the OV7 fusion polypeptide is onchocerca-specific and is recognized specifically by sera from onchocerciasis patients, and sera from non-patent but infected chimpanzees, and not by sera from patients with other filarial parasites, it may have potential as an antigenic component in a test for detection of non-patent and patent infections of O. volvulus. The OV7 amino acid sequence contains residues that have a probable homology with the cysteine proteinase inhibitor superfamily.

Gene organization of oryzacystatin-II, a new cystatin superfamily member of plant origin, is closely related to that of oryzacystatin-I but different from those of animal cystatins

The gene structure of oryzacystatin-II, a new cystatin superfamily member of rice seed origin, was determined. It spans approximately 2.5 kbp and comprises 3 exons. The number of exons and the intron-breakpoints coincide with those of oryzacystatin-I, the first well-defined plant cystatin. However, no similar sequences were observed between the two oryzacystatin genes in 5'-upstream regulatory regions, even though both are expressed specifically during the ripening stage of rice seeds. The gene organization of these two plant cystatins is generally different from that of animal cystatins.

The effect of adrenergic agonists and antagonists on cysteine-proteinase inhibitor (cystatin) in rat saliva

The effect of a number of adrenergic agonists and antagonists on the induction of rat salivary cystatin was investigated. A highly sensitive and specific radioimmunoassay was used to determine cystatin in rat whole saliva. Treatment for 10 consecutive days with a non-specific beta-adrenergic agonist isoproterenol, or the beta 1-adrenergic agonists dobutamine or methoxyphenamine, resulted in the induction of the salivary cystatin. Induction was also found in rats treated for 10 days with arterenol. Only trace quantities of cystatin could be detected in saliva of rats treated with the beta 2-adrenergic agonists terbutaline or salbutamol. When isoproterenol was injected concomitantly with the mixed beta-antagonist propranolol or the beta 1-adrenergic antagonists metaprolol, proctocol or atenolol the production of cystatin was totally suppressed. However, the beta 2-antagonist, ICI 118551, produced only a partial reduction in salivary cystatin induction elicited by isoproterenol. The findings suggest that the induction of salivary cystatin is regulated, in part, by beta 1-adrenergic receptor stimulation.

Sequence analysis, and chromosomal localization of a gene encoding a cystatin-like protein from Drosophila melanogaster

Using polyclonal antibodies raised against a Drosophila Ca2(+)-binding protein (DCABP-23), clones were isolated from a Drosophila head cDNA library constructed in the expression vector lambda gt11. Two non-homologous clones have been isolated and are being subjected to sequence analysis. One of these clones, though not encoding DCABP-23, does encode a Drosophila cystatin-like protein. This presumed Drosophila cystatin shows homology to mammalian cystatins, chicken egg white cystatin and the rice oryzacystatin. The Drosophila cystatin has been mapped, by in situ hybridization, to region 88C on the right arm of the third chromosome.

Direct radioimmunoassay of rat cystatin C: increased urinary excretion of this cysteine proteases inhibitor during chromate nephropathy

Rat cystatin C was purified to apparent homogeneity from rat urine after induction of a tubular dysfunction with sodium chromate. The two-steps purification procedure included a Carboxymethyl-papain affinity chromatography and anion exchange chromatography. The purified protein was identified as rat cystatin C by the following criteria: firstly retained on a Cm-papain affinity column, secondly an apparent molecular weight of 15 kDa and pI of 10.2. Antisera raised in rabbits against our purified rat cystatin C did not cross-react with other urinary proteins such as rat albumin and rat kallikrein, but partially cross-reacted with human cystatin C. A direct radioimmunoassay was developed and it enabled 8.32 fmol/ml of rat cystatin C to be detected. The detection range was between 0.125 and 62.5 ng/ml, with 10% intra-assay variation and 14% inter-assay variation. Physiological rat cystatin C excretion (40 +/- 18 micrograms/24 h) was found by the direct assay. In the chromate-intoxicated rat, urinary excretion increased twenty-fivefold (1017 +/- 391 micrograms/24 h) and returned to normal level one week after intoxication. This RIA will allow the study of rat cystatin C metabolism particularly during renal dysfunction.

Evolution of proteins of the cystatin superfamily

We have examined the amino acid sequences of a number of proteins that have been suggested to be related to chicken cystatin, a protein from chicken egg white that inhibits cysteine proteinases. On the basis of statistical analysis, the following proteins were found to be members of the cystatin superfamily: human cystatin A, rat cystatin A(alpha), human cystatin B, rat cystatin B(beta), rice cystatin, human cystatin C, ox colostrum cystatin, human cystatin S, human cystatin SA, human cystatin SN, chicken cystatin, puff adder cystatin, human kininogen, ox kininogen, rat kininogen, rat T-kininogens 1 and 2, human alpha 2HS-glycoprotein, and human histidine-rich glycoprotein. Fibronectin is shown not to be a member of this superfamily, and the c-Ha-ras oncogene protein p21 (Val-12) probably is not a member also. It was convenient to divide members of the superfamily into four types on the basis of the presence of one, two, or three copies of cystatin-like segments and the presence or absence of disulfide bonds. Evolutionary dendrograms were calculated by three methods, and from these we have constructed a scheme depicting the sequence of events in the evolution of these proteins. We suggest that about 1000 million years ago a precursor containing disulfide loops appeared, and that all disulfide-containing cystatins are derived from this. We follow the evolution of the proteins of the superfamily along four main lineages, with special attention to the part that duplication of segments has played in the development of the more complex molecules.

Cloning and sequence analysis of the genomic DNA fragment encoding oryzacystatin

A genomic DNA clone encoding oryzacystatin (Oc), a cysteine proteinase inhibitor (cystatin) of rice, was isolated from a lambda EMBL3 phage library constructed with Sau3AI partial digests of rice chromosomal DNA, by screening with an oc cDNA as a probe. The restriction map of the isolated DNA fragment was consistent with the pattern of the genomic Southern-blot analysis using a cDNA probe, and consequently, the gene is considered to be a single-copy gene. The oc gene is about 1.4 kb long and composed of three exons and two introns. The first intron (336 bp) intervenes between Ala-38 and Asp-39. The second intron (372 bp) exists in the 3'-noncoding region at the G residue next to the stop codon. S1 nuclease mapping showed the major transcription start point (tsp) at A, 104 bp upstream from the start codon (ATG). Typical CAT and TATA box sequences were found in the 5'-upstream region of the tsp. The nucleotide sequences around the TATA box, the tsp, the start codon, and the stop codon essentially matched the consensus sequences of other higher plant genes. The intron boundaries of the oc gene were quite different from those of the human kininogen-encoding gene and the human salivary cystatin (cystatin S)-encoding gene.

Primary structure of a new cysteine proteinase inhibitor from pig leucocytes

The primary structure of a pig leucocyte cysteine proteinase inhibitor, also called cathelin, was determined. The sequence was obtained from analyses of peptides isolated from the chymotryptic, endoproteinase Lys-C and protease V8 digests, and by analysis of the peptides derived from the hydrolysis of the aspartyl-prolyl bond of the carboxymethylated inhibitor. The inhibitor consists of 96 residues. The N-terminal residue of the inhibitor is pyrrolidone-carboxylic acid. The amino acid sequence of cathelin suggests the appearance of a new family of cysteine proteinase inhibitors.

Amino acid sequence of an inducible cysteine proteinase inhibitor (cystatin) from submandibular glands of isoproterenol-treated rats

We have previously reported the purification of an inducible cysteine proteinase inhibitor from submandibular glands of isoproterenol-treated rats by sequential gel filtration and ion-exchange chromatography [G. S. Bedi (1989) Arch. Biochem. Biophys. 270, 335-343]. This inhibitor is not detected in normal rat tissues but is induced in submandibular glands following beta-adrenergic stimulation of rats. In this study the complete amino acid sequence and the position of disulfide bridges of the purified protein were determined by automated Edman degradation of the protein and its tryptic, chymotryptic, and Staphylococcus aureus V8 protease peptides and were as follows: (sequence; see text) Computer analysis revealed the presence of 40-50% sequence identity between inducible cysteine proteinase inhibitor and cystatins from human saliva, human cystatin C, bovine cystatins, and chicken cystatins, all members of Family 2 cystatins. The inhibitor has little sequence similarity with rat liver and epidermal cysteine proteinase inhibitors, which belong to Family 1 cystatins.

Molecular cloning of cDNA for sarcocystatin A and analysis of the expression of the sarcocystatin A gene during development of Sarcophaga peregrina

Sarcocystatin A is a cysteine proteinase inhibitor purified from the hemolymph of Sarcophaga peregrina larvae [Suzuki, T., & Natori, S. (1985) J. Biol. Chem. 260, 5115-5120]. We isolated a cDNA clone for sarcocystatin A and analyzed the structure and expression of the sarcocystatin A gene. Sarcocystatin A consists of 102 amino acid residues. Significant homology was found between amino acid sequences of sarcocystatin A and other mammalian cystatins, and highly conserved sequences among mammalian cystatins were also found in sarcocystatin A. Using cloned cDNA as a probe, we investigated expression of the sarcocystatin A gene during the development of Sarcophaga. Results showed that this gene was transiently activated in the very early embryonic stage and in the pupal stage, suggesting that sarcocystatin A participates in morphogenesis of larval and adult structures of Sarcophaga.

A rapid two-step purification of rat cystatin C, one major inhibitor of cysteine proteinases

Rat cystatin C was purified to apparent homogeneity from rat urine after induction of a tubular dysfunction with sodium chromate. Twentyfold concentrated urine was chromatographed by a rapid purification procedure. A two-step purification including affinity chromatography on carboxymethyl papain- Sepharose and high-resolution anion exchange chromatography was developed. The purified protein has an apparent molecular mass of 15 kDa and pI of 10.2; its aminoacid composition was similar to human cystatin C. As opposed to previous data, purified urinary rat cystatin C did not contain significant amounts of carbohydrate. Antisera against rat cystatin C, raised in rabbits, partially cross-reacted with human and mouse cystatin C, indicating their antigenic similarities. Like human cystatin C, native rat cystatin C, named slow form, is degraded into a more acidic form, called fast form, by a loss of N-terminal amino acids; fast form displayed a pI of 9.4.

Internally repeated sequences in ras gene products

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Two rat homologues of human cystatin C

Two immunochemically related forms of cystatin C-like inhibitors which differ in their Mr app and isoelectric point have been found both in urine and seminal vesicles of rats. Amino-terminal sequences of these two cystatins are identical within the same fluid and exhibit a high degree of homology with that of human cystatin C. However, cystatins C purified from urine lack eight residues at their amino-terminal end when compared to those of seminal vesicles. The occurrence of two cystatin C-like components in rat fluids has been found to be due to the presence of a glycosylated form reported here as cystatin Cg which specifically binds concanavalin A and is susceptible to endo-beta-N-acetylglucosaminidase treatment.

Cystatin domains in alpha-2-HS-glycoprotein and fetuin

We have found that chain A of alpha-2-HS-glycoprotein contains two cystatin domains that show closest similarity to those of kininogen. Most likely, the two proteins diverged after the primary duplication of a single cystatin domain as the two cystatin domains of alpha-2-HS-glycoprotein are more similar, especially in disulfide bonding, to the corresponding domains of kininogen than to each other. We also propose that the carboxyl-terminal (non-cystatin) parts of kininogen and alpha-2-HS-glycoprotein contain homologous segments. We suggest that alpha-2-HS-glycoprotein may act as an inhibitor of the cysteine proteinases responsible for bone resorption. We have also found that fetuin is closely related to alpha-2-HS-glycoprotein.

Arrangement of the disulphide bridges in human low-Mr kininogen

The arrangement of the disulphide bridges in human low-Mr kininogen has been elucidated. Low-Mr kininogen contains 18 half-cystine residues forming nine disulphide bridges. The first and the last half-cystine residues of the amino acid sequence form a disulphide loop which spans the heavy- and the light-chain portion of the kininogen molecule. The other 16 half-cystine residues are linked consecutively to form eight loops of 4-20 amino acids; these loops are lined up in the heavy-chain portion of the kininogen molecule. In this way, a particular pattern of disulphide loops is formed which seems to be of critical importance for the inhibitor function of human kininogen.

Histidine-rich glycoprotein is evolutionarily related to the cystatin superfamily. Presence of two cystatin domains in the N-terminal region

A new member of the cystatin superfamily is introduced. Human plasma histidine-rich glycoprotein (HRG) was found to contain 2 cystatin-like sequences in tandem in the N-terminal region. Domain 1 (residues 1-112) was most homologous to domain 1 of the heavy chain of human kininogen and domain 2 (residues 113-225) was most homologous to human cystatin S as well as other cystatins and domain 3 of the heavy chain of kininogen, suggesting that the cystatin domains of HRG may represent a hitherto unknown binary form (or intermediate molecule) composed of 2 cystatin domains, and evolutionarily intermediate between the cystatin and the kininogen families.

Isolation and characterization of a cDNA coding for human myeloperoxidase

A cDNA encoding the carboxyl-terminal fragment of the human myeloperoxidase heavy chain was isolated and characterized. It was then used to determine the locations of the myeloperoxidase light and heavy chains in the polypeptide precursor. A cDNA library from poly(A)+ RNA from human leukemia HL-60 cells was constructed in pBR322 and screened by differential hybridization with enriched and depleted cDNA probes and then by hybridization with an oligonucleotide probe. A cDNA clone containing 1278 bp with an open reading frame of 474 bp and a 3' noncoding region of 804 bp was isolated. The amino acid sequence deduced from the nucleotide sequence consisted of 158 residues including a sequence of 14 amino acids known to be present in the heavy chain of the molecule. The cDNA also included a stop codon of TAG followed by a noncoding sequence that included a potential recognition site for polyadenylylation and a poly(A) tail. RNA transfer blot analysis with the cDNA probe indicated that myeloperoxidase mRNA was approximately 3.3 kb in length. In vitro translation of the mRNA selected by cDNA hybridization revealed preferential synthesis of a 74,000-Da polypeptide precursor that could be precipitated with anti-myeloperoxidase IgG. Antibodies specific for the heavy and light chains of myeloperoxidase were isolated from antiserum by affinity chromatography employing Sepharose columns covalently bound to the heavy or light chains. Antibodies specific for the light chain or the heavy chain readily precipitated the 74,000-Da precursor polypeptide. These results indicated that myeloperoxidase is synthesized as a single chain which undergoes processing into a light and heavy chain. Furthermore, the heavy chain of myeloperoxidase originates from the carboxyl terminus of the precursor polypeptide.

c-Ha-ras gene products are potent inhibitors of cathepsins B and L

c-Ha-ras proteins produced by Escherichia coli inhibited the activities of cathepsins B and L which had been partially purified from rat kidney. Furthermore, amino acid sequence homology between c-Ha-ras proteins and thiol proteinase inhibitors has been found.