Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q07644 (polypeptide)
 72,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

C1r was isolated from serum by an improved method and found to be a glycoprotein with a sedimentation coefficient of 7.0S. Under conditions of physiologic ionic strength and pH, C1r consist of two apparently identical noncovalently linked 95,000 dalton polypeptide chains. Antisera to C1r detected a protein of gamma-mobility on electrophoresis of serum in agarose in the presence of calcium, and a Beta-mobility protein when the electrophoretic separation was carried out in EDTA. On sucrose gradient ultracentrifugation of normal human serum in the presence of calcium, C1r antigenicity was found in the 19 S region of the gradient. On the other hand, when the gradient contained EDTA, C1r antigenicity was found in the 7 S region. No reaction of anti-C1r with C1r-deficient sera was observed. C1r had a high affinity for active C1s or proenzyme C1s in the presence of calcium and was able to activate C1s and to form C1 in conjunction with C1q and C1s. Activation of C1s by C1r was inhibited by calcium, C1 inactivator, polyanethol sulfonate, and DFP. Activation of C1s by C1r occurred only after a preliminary incubation of C1r for a brief time at 37 degrees C before addition of C1s. The ability of C1r to form C1 in conjunction with C1q and C1s was, however, progressively lost on incubation at 37 degrees C. Trypsin, although potentiating the activity of crude C1r, did not modify the activity of purified C1r. Its action was on a trypsin-sensitive inhibitor separated from C1r in the final step of the isolation procedure. The binding of 125I-C1r to sensitized sheep erythrocytes required the presence of C1q and calcium but not C1s, whereas the binding of 125I-C1s required C1q, C1r and calcium. Thus, C1r functions as not only the activator of C1s, but also serves as the physical link between C1q and C1s in macromolecular C1.
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PMID:Physicochemical and functional characterization of the C1r subunit of the first complement component. 81 63

Exposure of Fc fragments derived from human IgG1 myeloma proteins to acid pH rendered the region between the Cgamma2 and Cgamma3 domains transiently susceptible to cleavage by trypsin upon return to neutral pH. Trypsin covalently linked to Sepharose was used and two fragments derived from the Cgamma2 region and one from the Cgamma3 region were purified by column chromatography. On the basis of amino acid analysis, primary sequency data, antigenic properties, and m.w., one of the Cgamma2 fragments was shown to consist of two polypeptide chains of unequal mass joined by the inter-heavy chain disulfide bonds. The larger chain corresponded to a stretch of gamma-chain between Thr 223 and Lys 338 (Eu numbering) and the shorter chain to the section between Thr 223 and Lys 248. The other Cgamma2-fragment was a disulfide-linked dimer of the Thr 223 to Lys 338 sections of the paired gamma-chains. When this latter fragment was reduced under mild conditions it dissociated into monomers indicating that there was little or no noncovalent interactions between the Cgamma2 domains. The Cgamma3-fragment was shown to be a noncovalent dimer composed of the Glu 345 to Lys 349 sections of the two gamma-chains although some heterogeneity was apparent at the amino-terminus. Circular dichroism was used to probe the conformational relationships between the isolated domains and the parent Fc. The spectral properties of Fc could not be fully accounted for on the basis of the spectra observed for the isolated domains which suggested that inter-domain interaction might be significant in Fc.
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PMID:Structure and function of immunoglobulin domains. III. Isolation and characterization of a fragment corresponding to the Cgamma2 homology region of human immunoglobin G1. 81 64

ATP citrate lyase was purified by two different procedures from the livers of rats first starved and then fed with a fat-deficient and high carbohydrate-glycerol diet. These enzyme preparations were judged homogeneous by sedimentation equilibrium and polyacrylamide gel electrophoresis. The molecular weight of the native enzyme was around 4.4 X 10(5) as determined by sedimentation equilibrium. On sodium dodecyl sulfate gel electrophoresis the enzyme usually showed a single protein band with an estimated molecular weight of 1.2 X 10(5). A similar value for the molecular weight of the subunit was obtained by gel filtration on 6% agarose in the presence of 6 M guanidinium chloride. The molecular weight of this polypeptide chain was estimated by sedimentation equilibrium to be around 1.1 X 10(5). These results indicated that ATP citrate lyase has a subunit structure of four polypeptides of similar size. The extinction coefficient of the dry protein and its amino acid composition are also reported. Some batches of fully active enzyme, judged to be homogeneous by sedimentation equilibrium and polyacrylamide gel electrophoresis, showed two additional major polypeptides (Mr approximately 7.1 X 10(4) and 5.5 X 10(4)) on sodium dodecyl sulfate gel electrophoresis. Studies on the polypeptides produced by proteolytic modification of the native enzyme by trypsin indicated that the additional protein bands observed on sodium dodecyl sulfate gel electrophoresis with some of the batches of enzyme could have been formed by limited proteolysis ("nicking") of the original 1.1 X 10(5) subunit. Trypsin treatment of the native enzyme did not affect the enzyme activity, whereas chymotrypsin and pronase treatment inactivated the enzyme. The trypsin-treated enzyme, which contained only the two smaller polypeptides, did not differ significantly from the untreated enzyme with respect to sedimentation behavior, phosphorylation by ATP, Km for citrate, and immunoreactivity, but it was more heat-labile than the untreated enzyme. The phosphate group on the phosphorylated "nicked" enzyme was located on the larger polypeptide fragment.
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PMID:Structure of ATP citrate lyase from rat liver. Physicochemical studies and proteolytic modification. 82 50

The kinetics of cleavage of C3 by trypsin was analyzed by electrophoresis in agarose and in polyacrylamide gels containing sodium dodecyl sulfate and the data obtained were used to construct an anatomical model for C3 showing the sites of tryptic attack, the fragments generated, and their composition. Trypsin was shown to cleave C3 in a stepwise fashion. The attack was initially directed at the alpha-polypeptide chain and resulted in the generation of C3a and C3b. Further cleavage of the alpha-chain of C3b, converted it into C3b1 and then into C3d and C3c. Cleavage of the beta-chain by trypsin occurred only at the C3c stage with the release of a small peptide (m.w. 12,000) from C3c and the formation of C3c'. On immunoelectrophoresis, C3c' had a less anodal mobility compared to the beta1A mobility of C3c. C3a, once formed could be further cleaved to give residual fragments with decreasing net positive charge. Exposure of C3 to acid conditions, pH 5.0 or below, rendered the molecule exceedingly susceptible to tryptic degradation.
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PMID:Kinetic studies on the fragmentation of the third component of complement (C3) by trypsin. 86 57

A coagulogen in Limulus lysate has been purified to apparent homogeneity as judged by sodium dodecyl sulfate-gel electrophoresis. The purified coagulogen identified by its ability to clot with either trypsin or the purified Limulus clotting enzyme (Tai, J.Y., and Liu, T. Y. (1976) Fed. Proc. 35, 1486) has a molecular weight of 24,500. It consists of a single polypeptide chain of about 220 amino acids with glycine and serine as its NH2- and COOH-terminal residues; respectively. When acted upon by the Limulus clotting enzyme, the coagulogen releases a soluble C-peptide of about 45 amino acids and an insoluble coagulin of about 170 amino acids. The latter interacts in a noncovalent fashion to form the clot. Amino acid analyses together with the results of NH2- and COOH-terminal analyses suggest that the clot formation involves the cleavage of an--Arg--Lys--bond. Trypsin acts on the coagulogen to cause clotting by splitting the same peptide bond.
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PMID:Studies on Limulus amoebocyte lysate II. Purification of the coagulogen and the mechanism of clotting. 87 16

Trypsin inhibitor was isolated from seeds of opaque-2 corn by affinity chromatography on a trypsin/Sepharose column. The two major forms of inhibitor eluted from the affinity column were separated by DEAE-cellulose chromatography in the presence of urea. One form of inhibitor is a single-chain protein that has a molecular weight of approximately 12,500; the second inhibitor has two polypeptide chains and appears to have been produced from the single-chain inhibitor by exposure to trypsin in the affinity chromatography step. The relationship of the inhibitor isolated from opaque-2 corn to an inhibitor previously isolated from an unspecified strain of maize by Hochstrasser et al. (Hochstrasser, K., Muss, M., and Werle, E. (1967) Z. Physiol. Chem. 348, 1337-1340) is discussed.
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PMID:Isolation and characterization of trypsin inhibitor from opaque-2 corn seeds. 91 65

Milk fat globule membrane was solubilized with sodium dodecyl sulfate and mercaptoethanol and the membrane proteins were separated by SDS-polyacrylamide gel electrophoresis. The membrane preparations contained three major size classes of polypeptide of 155,000, 62,500 and 43,500 daltons. At least five glycopeptides were separated of which two stained intensely with periodic acid-Schiff reagent, but poorly with coomassie blue. Trypsin hydrolysis of whole cream and isolated milk fat globule membrane revealed major differences in the rates of protein hydrolysis. Many of the membrane proteins of whole cream resisted proteolysis compared with the same proteins in the isolated membrane. Two glycopeptides were resistant to trypsin digestion in either preparation. Treatment of whole cream with neuraminidase led to the release of at least 70% of the protein-bound sialic acid. Whole cream and isolated membrane samples were iodinated with 125I in the presence of lactoperoxidase and hydrogen peroxide. The membrane proteins were significantly more accessible to lactoperoxidase-125I i in isolated membrane compared with the proteins of whole cream. Polypeptides of molecular weight 43,500 and approximately 48,000 daltons were predominantly labelled in whole cream and could be eluted from the fat globules with magnesium chloride (1.5m). The results strongly suggest that the proteins of milk fat globule membrane are asymmetrically arranged in the membrane and that most of the protein-bound sialic acid is present on the external surface of milk fat globules.
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PMID:Studies on the structure of milk fat globule membrane. 119 40

C1r was unable to cleave and activate proenzyme C1s unless first incubated at 37 degrees C in the absence of calcium before the addition of C1s. The acquisition of ability to activate C1s was associated with, and paralleled by, cleavage of each of the two noncovalently bonded 95,000 dalton chains of the molecule into disulfide linked subunits of 60,000 and 35,000 daltons, respectively. Thus, C1r is converted from an inactive form into an enzyme, C1r, able to cleave and activate C1s by proteolytic cleavage in marked analogy to the activation of several other complement enzymes. Trypsin was also found to cleave C1r but at a different site, and its action did not lead to C1r activation. C1r activation was inhibited by calcium, polyanethol sulfonate, C1 inactivator, and DFP but not by a battery of other protease inhibitors. C1 inactivator inhibited C1r by forming a complex with C1r via sites located on the light chain of the molecule. In other studies, cleavage of C1r was not accelerated by the addition of C1r ot C1s. C1r and C1r were found to have the same m.w., sedimentation coefficient, and diffusion coefficients. They differed, however, in charge with C1r migrating as a Beta-globulin and C1r as a gammaglobulin on electrophoresis in agarose. The amino acid composition of C1r and of each of the two polypeptide chains of Clr was determined. Both chains contained carbohydrate. Proteolytic cleavage of the C1r molecule was found to occur on addition of aggregated IgG to a mixture of C1q, C1r, and C1s in the presence of calcium. Neither C1q, C1s nor aggregated IgG alone, not C1r nor C1s induced C1r cleavage. Liquoid, an inhibitor of C1 activation, inhibited C1r cleavage. Thus, proteolytic cleavage of C1r appears to be a biologically meaningful event occurring during the activation of C1.
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PMID:Activation of C1r by proteolytic cleavage. 124 22

Band 3 is the major, membrane-spanning, approximately90 000 dalton polypeptide of the human erythrocyte membrane. To facilitate the analysis of its structural integration into the membrane, we have cleaved this protein in situ into large fragments and ascertained their disposition. Digestion of intact cells with chymotrypsin yielded band 3 fragments with apparent molecular weights of 38 000 and 55 000. Both fragments resisted elution by NaOH and acetic acid, suggesting that they are anchored in the apolar core of the membrane. Both pieces communicate with the extracellular space, and the 55 000 dalton species extends to the cytoplasmic surface as well. Digestion of unsealed ghosts with chymotrypsin produced a hydrophobic 17 000 dalton species, a segment of the 55 000 dalton fragment, which spans and is firmly anchored in the core of the membrane. Trypsin and papain at low concentration generated integral band 3 fragments of 52 000 daltons and released major band 3 fragments of less than or equal to 41 000 daltons from the cytoplasmic side of the membrane. The latter water-soluble polypeptides remained associated in discrete complexes which retained the capacity to bind glyceraldehyde-3-phosphate dehydrogenase. An interchain disulfide bond, which can be induced only at the cytoplasmic surface, cross-linked intact band 3, and certain of its water-soluble fragments. Finally, fragments of 23 000 daltons were generated from the innersurface domain by reacting disulfide-linked band 3 dimers with cyanide or reduced polypeptides with 2-nitro-5-thiocyanobenzoate. A provisional ordering of these fragments is proposed.
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PMID:Proteolytic dissection of band 3, the predominant transmembrane polypeptide of the human erythrocyte membrane. 125 33

The topography of the Aleutian mink disease parvovirus (ADV) G virion was analyzed with monoclonal antibodies and polyclonal antiserum. There was homology between the two major structural proteins as others have previously reported. Trypsin treatment of the virion with subsequent immunoblotting revealed that VP2 represents the main peptide on the exterior of virion and that VP1 is probably embedded within the capsid. Additional analyses of the trypsin-treated virions showed that VP2 is responsible for binding complement and that it also represents the structural part of the virion that binds to cellular receptors. A third protein, p34, was detected that might represent a third structural polypeptide because of its many unique epitopes relative to the other peptides detected.
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PMID:Topographical analysis of the G virion of Aleutian mink disease parvovirus with monoclonal antibodies. 128 Sep 44


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