Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.21.1 (chymotrypsin)
10,938 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Treatment of phosphorylated chicken gizzard myosin which had incorporated 1.5 mol of phosphate per 4.7 x 10(5) g of protein with 1-fluoro-2,4-dinitrobenzene resulted in the modification of the heavy and light chains when 5.8 mol of the reagent were bound to myosin. Concurrently, the K+-ATPase activity was inhibited and the modified myosin possessed actin activated-ATPase activity. Thiolysis of nearly 2 mol of the dinitrophenyl group mainly from the heavy chains (and some light chains) of the modified myosin with 2-mercaptoethanol restored the K+-ATPase activity. Digestion of phosphorylated gizzard myosin with chymotrypsin or papain occurred to a lesser extent than a control myosin. Chymotryptic fragments of phosphorylated and dinitrophenylated myosin were formed at a faster rate than those of dinitrophenylated myosin alone suggesting that phosphorylation of the light chain of Mr 20,000 altered the susceptibility of the heavy chains of myosin to proteolysis. Phosphorylation of dinitrophenylated gizzard myosin which had incorporated 5.5 mol of 1-fluoro-2,4-dinitrobenzene per 4.7 x 10(5) g of protein was the same as that of a control myosin; this was also the case for the thiolyzed dinitrophenylated myosin. In the absence of calcium, phosphorylation of control and dinitrophenylated myosins decreased by 73% suggesting that the phosphorylation reaction was calcium dependent. Phosphorylation and dinitrophenylation induced conformational changes in the light chains of gizzard myosin that may be involved in maintaining the structure of the heavy chain region.
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PMID:Effect of phosphorylation and dinitrophenylation on chicken gizzard myosin. 622 21

The experiments in this report, together with previous studies, demonstrate that the light chains of DR antigens are composed of four domains: two large extracellular domains (each with a disulfide loop), a short hydrophobic membrane-binding region, and a short hydrophilic carboxy-terminal domain. The amino-terminal extracellular domain is glycosylated and polymorphic and has no discernible sequence homology to immunoglobulin, whereas the relatively conserved carboxy-terminal extracellular domain bears striking homology to immunoglobulin. One chymotryptic and two tryptic cleavage sites lie in the second extracellular domain of the light chain of all native DR antigens. These three sites are found in loops at the same end of an immunoglobulin-like domain. The light chain of DC1 antigen lacks one of the tryptic cleavage sites; the DR heavy chain, the class I heavy chain, and beta 2 microglobulin lack all three proteolytic sites. Proteolysis of murine la antigens with chymotrypsin and trypsin generates similar fragments (I-E-like DR, I-A-like DC1) suggesting these cleavage sites are a general feature of class II antigen light chains.
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PMID:The extracellular region of light chains from human and murine MHC class II antigens consists of two domains. 640 6

The 130- and 125-kDa heavy chains of Acanthamoeba myosins IA and IB were radioactively labeled at either the regulatory phosphorylation site or the catalytic site and then subjected to controlled proteolysis by either trypsin or chymotrypsin. The labeled and unlabeled peptides generated during the course of proteolysis were identified by autoradiography and Coomassie Blue staining after separation by electrophoresis on sodium dodecyl sulfate-polyacrylamide gels. The relative positions of the phosphorylation and active sites could be deduced. The catalytic site of myosin IA is most probably within 38 kDa of one end of the 130-kDa heavy chain, and the phosphorylation site, which can be no more than 40 kDa away from the catalytic site, would then be between 38 and 78 kDa of that same end of the heavy chain. Possibly, the phosphorylation site is further restricted to the region between 38 and 64 kDa from the end of the heavy chain. The catalytic and phosphorylation sites of myosin IB are both contained within a segment of 62 kDa at one end of the 125-kDa heavy chain and are within 40 kDa of each other. The phosphorylation site may be restricted to a small segment between 60 and 62 kDa from one end of the heavy chain which would limit the possible position of the catalytic site to the region between 20 and 60 kDa of that end.
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PMID:Localization of the active site and phosphorylation site of Acanthamoeba myosins IA and IB. 650 Dec 93

Human factor XII was activated by limited proteolysis with trypsin, and the resulting beta-factor XIIa (Mr = 30,000) was isolated by DEAE-Sephacel column chromatography. The complete amino acid sequence of beta-factor XIIa was then determined on peptides produced by enzymatic digestion with either trypsin, chymotrypsin, or Staphylococcus aureus V8 protease and by chemical cleavage at methionyl and tryptophyl bonds. beta-Factor XIIa is a glycoprotein composed of a heavy chain (243 amino acid residues) and a light chain (9 amino acid residues), and these two chains are held together by a disulfide bond. The carbohydrate is attached to asparagine residue 61 in the heavy chain. The amino acid sequence of the heavy chain shows a high degree of homology to the corresponding regions of other plasma serine proteases, such as plasmin, thrombin, factor IXa and factor Xa, as well as the pancreatic digestive enzymes. These results demonstrate that factor XII is the precursor of a typical serine protease that participates in the coagulation cascade.
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PMID:Amino acid sequence of human beta-factor XIIa. 660 55

The patterns of myosin isozymes in embryonic and adult chicken pectoralis muscle were examined by electrophoresis in a non-denaturing gel system (pyrophosphate acrylamide gel electrophoresis), and both light chains and heavy chains of embryonic and adult myosin isozymes were compared. In pyrophosphate acrylamide gel electrophoresis, the predominant isozyme component in embryonic pectoralis myosin could be clearly distinguished from adult myosin isozymes. SDS-polyacrylamide gel electrophoresis indicated that the light chain composition of embryonic myosin was also different from that of adult myosin. The pattern of peptide fragments produced by myosin digestion with a-chymotrypsin differed significantly between embryonic and adult skeletal myosin. These results suggest that myosin in the embryonic pectoralis muscle is different in both light and heavy chain composition from myosin in the same adult tissue.
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PMID:Changes in myosin isozymes during development of chicken breast muscle. 680 70

The distribution of myosin isozymes in embryonic and adult chicken gizzard muscle were examined by electrophoresis in a non-denaturing gel system (pyrophosphate acrylamide gel electrophoresis), and both light and heavy chains of embryonic and adult myosin isozymes were compared. In pyrophosphate acrylamide gel electrophoresis, there were three isozyme components in embryonic gizzard myosin, but only one isozyme in adult gizzard myosin. The mobility of the fastest migrating embryonic isozyme was similar to that of the adult isozyme. The three embryonic isozymes differ from each other in the light chain distribution. Two of them contain an embryo-specific myosin light chain, which is characterized by its molecular weight and isoelectric point, whereas the other embryonic myosin isozyme contained the same light chains as the adult myosin. The pattern of peptide fragments of embryonic heavy chain produced by digestion with alpha-chymotrypsin in the presence of SDS was not distinguishable from that of adult myosin heavy chain. Thus there are myosin isozymes specific to embryonic gizzard muscle which exhibit embryo-specific light chain compositions, but are similar to adult gizzard myosin in their heavy chain structure.
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PMID:Changes in myosin isozymes during development of chicken gizzard muscle. 687 71

Evidence is presented that the removal of the alkali light chain subunit from myosin subfragment 1 results in the exposure of a site (or sites) at the carboxyl-terminal region of the heavy chain that is rapidly digested by both trypsin and alpha-chymotrypsin. In the case of trypsin digestion, cleavage at this site proceeds at a much higher rate than cleavage at the two other sensitive regions located in the interior of the primary structure of this chain. This initial cleavage is responsible for the generation, on further digestion with trypsin, of a carboxyl-terminal fragment about 3000 daltons smaller than the corresponding fragment formed by digestion of subfragment 1. The ability of the heavy chain to reassociate with alkali light chain at 4 degrees C in the presence of MgATP is essentially abolished by cleavage at this exposed site by either trypsin or chymotrypsin. These observations indicate that the alkali light chain is binding to, or is capable of perturbing, a region of the heavy chain adjacent to the subfragment 1/subfragment 2 "hinge" region and support recent proposals that both the DTNB light chain and the alkali light chain may be interacting and may be modulating this flexible region of the cross bridge.
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PMID:On the mode of the alkali light chain association to the heavy chain of myosin subfragment 1. Evidence for the involvement of the carboxyl-terminal region of the heavy chain. 688 36

A model has been constructed for haptoglobin heavy chain by using the known sequence homology to the mammalian serine proteases. The three-dimensional structures for three serine proteases, chymotrypsin, trypsin, and elastase, were compared and the structural features that are conserved in all three were extracted. The haptoglobin heavy chain sequence was aligned to the sequences of the three serine proteases by maximizing sequence homology in the regions of conserved structure. The resulting alignment shows that haptoglobin heavy chain must be very closely homologous to these proteases in structure as well as in sequence. Coordinates were derived for the heavy chain by using the homologous structures. The problems associated with these coordinates are outlined and methods for solving them are indicated. The features of the haptoglobin heavy chain structure are described. Implications of the structure for the very strong interaction between this subunit and hemoglobin are discussed.
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PMID:Model for haptoglobin heavy chain based upon structural homology. 693 26

A cDNA library prepared from human liver has been screened for factor IX (Christmas factor), a clotting factor that participates in the middle phase of blood coagulation. The library was screened with a single-stranded DNA prepared from enriched mRNA for baboon factor IX and a synthetic oligonucleotide mixture. A plasmid was identified that contained a cDNA insert of 1,466 base pairs coding for human factor IX. The insert is flanked by G-C tails of 11 and 18 base pairs at the 5' and 3' ends, respectively. It also included 138 base pairs that code for an amino-terminal leader sequence, 1,248 base pairs that code for the mature protein, a stop codon, and 48 base pairs of noncoding sequence at the 3' end. The leader sequence contains 46 amino acid residues, and it is proposed that this sequence includes both a signal sequence and a pro sequence for the mature protein that circulates in plasma. The 1,248 base pairs code for a polypeptide chain composed of 416 amino acids. The amino-terminal region for this protein contains 12 glutamic acid residues that are converted to gamma-carboxyglutamic acid in the mature protein. These glutamic acid residues are coded for by both GAA and GAG. The arginyl peptide bonds that are cleaved in the conversion of human factor IX to factor IXa by factor XIa were identified as Arg145-Ala146 and Arg180-Val181. The cleavage of these two internal peptide bonds results in the formation of an activation peptide (35 amino acids) and factor IXa, a serine protease composed of a light chain (145 amino acids) and a heavy chain (236 amino acids), and these two chains are held together by a disulfide bond(s). The active site residues including histidine, aspartate, and serine are located in the heavy chain at positions 221, 270, and 366, respectively. These amino acids are homologous with His57, Asp102, and Ser195 in the active site of chymotrypsin. Two potential carbohydrate binding sites (Asn-X-Thr) were identified in the activation peptide, and these were located at Asn157 and Asn167. The homology in the amino acid sequence between human and bovine factor IX was found to be 83%.
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PMID:Isolation and characterization of a cDNA coding for human factor IX. 695 30

The effects of the inhibitor of N-linked glycosylation, tunicamycin, on the synthesis of HLA-A and -B antigens in the human lymphoblastoid cell line JY are described. HLA-A and -B antigens are membrane glycoproteins that consist of a two chain complex, the heavy chain being glycosylated at Asn 86, whereas the light chain, identical to beta 2-microglobulin, is not glycosylated. HLA-A and -B antigens synthesized in the presence of the antibiotic are devoid of carbohydrate. This lack of carbohydrate does not affect the association of the heavy and light chains, nor does it affect the reactivity with human alloantisera, or a mouse monoclonal antibody W6/32, that reacts with all HLA-A and -B specificities examined so far. Nonglycosylated HLA-A and -B antigens are no more susceptible to proteolysis with trypsin, chymotrypsin, or papain than their fully glycosylated counterparts. Thus it may be concluded that the carbohydrate side chains of HLA-A and -B antigens do not contribute significantly to the conformation of HLA-A and -B antigens, at least as measured by these procedures. Pulse-chase experiments, in conjunction with the isolation of cell-surface HLA-A and -B antigens by adsorbing the monoclonal antibody W6/32 to intact cells, indicate that nonglycosylated molecules reach the cell surface at a rate indistinguishable from that of fully glycosylated molecules (although the absolute amount synthesized in the presence of tunicamycin was decreased). Thus glycosylation is also not required for membrane insertion of HLA antigens, nor for their subsequent transport to the cell surface.
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PMID:Biosynthesis and cell surface localization of nonglycosylated human histocompatibility antigens. 700 35


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