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)

The heavy chain fragmentation pattern of native myosin when digested by proteolytic enzymes is influenced by such conditions as the nature of the proteolytic agent, ionic strength and presence or absence of divalent cations. HMM and S-1 produced by digestion of 14CNEM-labelled myosin under various conditions were analyzed by sodium dodecyl-sulfate polyacrylamide gel electrophoresis. Purified samples of these species were digested under controlled conditions by chymotrypsin and trypsin and a comparison of the observed heavy chain fragmentation patterns led to a sequential arrangement of the proteolytic fragments. The main features of this arrangement are the following: a 21K molecular weight tryptic peptide is found at the N-terminal side of myosin heavy chain. Adjacent to it is a 48K peptide, then a 19.5K peptide containing the two SH-1 and SH-2 thiols. These three peptides constitute the heavy chain of S-1. Adjacent to this S-1 heavy chain is a tryptic (and also chymotryptic) 40K peptide. The rest of the HMM heavy chain on the C-terminus is a sequence susceptible to both chymotrypsin and trypsin attack yielding an undefined number of small peptides.
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PMID:Proteolytic fragmentation of myosin: location of SH-1 and SH-2 thiols. 11 42

1. Prolonged treatment of coupling factor I (CF1) from spinach chloroplasts with trypsin free of chymotrypsin yielded an active ATPase. The isolated preparation showed only two polypeptide chains (mol wt 55,000 to 60,000) on acrylamide gels run in the presence of sodium dodecyl sulfate. The three smaller subunits of CF1 were not detectable. The preparation no longer served as a coupling factor for photophosphorylation in either EDTA- or silicotungstate-treated chloroplasts. 2. An antiserum prepared against coupling factor I from chloroplasts inhibited the ATPase activity of the trypsin-treated CF1. In contrast, antisera prepared against the two individual (denatured) subunits did not inhibit the ATPase activity when tested either alone or together, although each interacted with the trypsin-treated protein, forming precipitin lines in Ouchterlony plates. 3. The trypsin-treated enzyme was still cold-labile, showing that the three smaller subunits are not required for this property. However, the enzyme was no longer sensitive to the natural inhibitor protein which is one of its subunits (subunit epislon), but was still sensitive to inhibition by the flavonoid quercetin. 4. Two equivalents of 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole were sufficient to inhibit about 80% of the ATPase activity of the coupling factor, irrespective of whether it contained two of five subunits. The inhibition was completely reversed by dithiothreitol. 5. Triated 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole was prepared. Treatment of the coupling factor with this tritium-labeled inhibitor followed by electrophoresis on acrylamide gels revealed that most of the radioactivity was incorporated into the beta subunit of the enzyme (molecular weight 56,000).
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PMID:Partial resolution of the enzymes catalyzing photophosphorylation. XV. Approaches to the active site of coupling factor I. 12 75

Twelve antigens were detected in crude group C streptococcal extracellular concentrates, using naturally occurring antibodies in normal human gamma globulin. These group C streptococcal antigens all appeared to be present in crude group A streptococcal extracellular concentrates, although the latter contained additional antigens reactive with the human antibodies. Systematic purification procedures were established for the isolation of the group C streptococcal antigens by a sequence of salting out, hydroxylapatite chromatography, Sephadex G-100 gel filtration, and isoelectric focusing. With such procedures, three of the group C streptococcal antigens were isolated in a relatively pure state. One of the purified antigens was identified as streptokinase on the basis of its fibrinolytic potency, its reaction of identity with two purified streptokinase fractions obtained from other sources, and its high titer in immunodiffusion assays. The most highly purified streptokinase fractions, derived from the 0.1 M sodium phosphate hydroxylapatite eluate, revealed a plasmin-inhibiting effect at high concentrations of streptokinase. This was not seen in the purified streptokinase of equivalent functional and immunological purity that was derived from the 0.2 M sodium phosphate hydroxylapatite peak. Two other streptococcal antigens were also isolated to a high degree during the course of the above study. These were designated antigens X and Y and were found to be unrelated immunologically to each other or to streptokinase. Their isoelectric points were 6.7 and 8.8, respectively, and both were present in group A streptococcal concentrates. Esterase activity was found to be widely distributed in almost all of the fractions obtained in the various purification steps, indicating a high degree of heterogeneity of the streptococcal enzyme. Histochemical staining techniques applied to the immune precipitates formed with human antibodies indicated that none of the antigens detected in crude group C and group A streptococcal concentrates possessed catalase, glucuronidase, glucosaminidase, acid or alkaline phosphatase, arylsulfatase, leucineaminopeptidase, or chymotrypsin enzymatic activities.
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PMID:Purification of group C streptococcal extracellular antigens detected with naturally occurring human antibodies: isolation of streptokinase and two previously undescribed antigens. 13 Nov 8

Purified (Na+, K+)-activated adenosine triphosphatase ((Na+, K+)-ATPase, ATP phosphohydrolase, EC 3.6.1.3) has been subjected to trypsin and chymotrypsin hydrolysis. The glycoprotein is much more resistant to proteolysis than the large chain. This differential susceptibility to proteolysis is not due to differences in the number of trypsin or chymotrypsin sensitive bonds because the two subunits are equally susceptible to proteolysis after isolation by preparative gel electrophoresis in sodium dodecyl sulfate. It is also not due to steric "shielding" of the glycoprotein by the large chain or its proteolytic products: (1) The rate of digestion of the glycoprotein is not increased after 90% of the large chain is digested. (2) The majority of the large chain peptides are released into the supernatant upon degradation. It is concluded that the greater resistance of the glycoprotein to proteolysis is due to its native conformation. In the absence of the large chain, the susceptibility of the glycoprotein to tryptic degradation by K+ and Na+. The evidence suggests that this decreased susceptibility was due to conformational changes in the glycoprotein. These specific ligand effects on proteolysis of the glycoprotein suggests that the glycoprotein may participate in Na+ and K+ binding by (Na+, K+)-ATPase.
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PMID:The susceptibility of the glycoprotein from the purified (Na+, K+)-activated adenosine triphosphatase to tryptic and chymotryptic degradation with and without Na+ and K+. 13 66

Studies have been conducted to characterize further the interaction between 125I-labeled bovine thyrotropin (TSH) and bovine thyroid plasma membranes. Sequential subcellular fractionation of thyroid homogenates yielded preparations of progressively greater specific binding activity, highest activity being found in fractions previously shown to contain predominately plasma membranes (Amir, S. M., Carraway, T.F., Kohn, L.D., and Winand, R.J. (1973) J. Biol. Chem. 248, 4092-4100). Although binding of 125I-TSH by plasma membranes was greatest at pH 6.0, studies were conducted at pH 7.45 as well as pH 6.0, and results obtained differed quantitatively, but not qualitatively. Binding was maximal at 0 degrees, 15 degrees, and 22 degrees and steady state values remained unchanged for at least 22 hours. At 37 degrees, binding was decreased by 40% at 1 hour; the loss was even greater (65%) at 50 degrees. A similar loss of binding was evident when membranes were preincubated without TSH at 37 degrees or higher and were then incubated with 125I-TSH at 0 degrees. Lineweaver-Burk analysis indicated that preincubation resulted in loss of receptor sites without change in affinity of residual receptors. Addition of Ca2+ (1 to 10 mM) to the preincubation medium prevented the effect of preincubation at 37 degrees by preserving the number of receptor sites without altering their affinity. Under similar conditions, Na+ and K+ were without protective effect. Membranes bound 45Ca2+ in a specific and saturable manner. Scatchard plots indicated a dissociatiion constant (Kd) of 9 X 10(-5) M and a capacity (n) of 54 nmol/mg of membrane protein. 45Ca2+ was also displaced from membranes by Mg2+ and Mn2+. Ca2+ had a biphasic effect on binding; low concentrations (1 to 10 muM) added to the incubation mixture stimulated binding, while higher concentrations (0.1 mM) caused inhibition. Mg2+ and Mn2+, at comparable concentrations, were also inhibitory, Na+ and K+ less so. In the case of Ca2+, both the stimulatory and inhibitory concentrations were lower than those required to achieve saturation of Ca2+-binding sites. Proteolytic enzymes (trypsin, alpha-chymotrypsin, and pronase) sharply reduced binding of 125I-TSH, owing to a decrease in receptor sites. Phospholipases A and C enhanced binding of TSH, while neuraminidase and beta-galactosidase were without measurable effect.
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PMID:Properties of the interaction between bovine thyrotropin and bovine thyroid plasma membranes. 18 81

Reaction of the cAMP (cyclic adenosine 3'--5'-monophosphate) receptor protein (CRP) of Escherichia coli with the bifunctional reagent o-phenylenedimaleimide (oPDM) results in the cross-linking of the two subunits of a CRP protomer. In the presence of cAMP the rate of cross-linking increases. CRP modified with oPDM retains [3H]cAMP binding activity but loses [3H]d(I-C)n binding activity. Proteolysis of cross-linked CRP gives distinct sodium dodecyl sulfate-polyacrylamide gel electrophoretic patterns depending upon whether cAMP was present during the reaction with oPDM. CRP cross-linked in the absence of cAMP retains the same relative resistance to proteolysis as unmodified CRP. The presence of 0.1 mM cAMP during proteolysis results in the production of two fragments, one of approximately 13 000 daltons and a second of approximately 20 000 daltons. CRP cross-linked with oPDM in the presence of cAMP (then dialyzed to remove cAMP) remains sensitive to alpha-chymotrypsin digestion even in the absence of added cAMP producing only the 13 000-dalton fragment. It is suggested that the nature of the oPDM cross-link is a consequence of the conformational state of CRP.
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PMID:Cross-linking of the cAMP receptor protein of Escherichia coli by o-phenylenedimaleimide as a probe of conformation. 21 22

Stereospecific high-affinity binding sites for beta h-[3H]endorphin could be demonstrated in the P2 pellet of rat brain homogenate. Scatchard analysis of the binding data revealed binding sites with Kd values of 0.81 and 6.8 nM and density of 120 and 240 fmol/mg of protein. Distribution of beta h-[3H]endorphin binding in various brain regions parallels that of opiate receptor:striatum greater than thalamus greater than amygdala greater than hypothalamus, septum greater than cortex greater than midbrain, brainstem. Similar to their effect on 3H-labeled agonist binding, Na+ and other monovalent cations, GTP, trypsin, chymotrypsin, phospholipase A2, and N-ethylmaleimide all inhibited the specific binding of beta h-[3H]endorphin. In contrast to their action on alkaloid and enkephalin binding, Ca2+, Mg2+, and Mn2+ also inhibited beta h-[3H]endorphin binding. These data suggest a difference between beta h-endorphin and alkaloid/enkephalin binding sites.
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PMID:Properties and localization of beta-endorphin receptor in rat brain. 23 Apr 77

Radiolabeled Sendai viral envelope proteins were incorporated into human erythrocyte membranes by the process of fusion of the viral envelope with the erythrocyte membrane. Inside-out (IO) vesicles were prepared from the erythrocyte membranes containing viral proteins, and the presence of viral proteins was assessed by electrophoresis in sodium dodecyl sulfate/polyacrylamide gels. Proteolysis with trypsin, chymotrypsin, or Pronase, which digests only the external surface of the IO vesicles (the cytoplasmic surface of the erythrocyte membrane) revealed that the viral nucleocapsid and the nonglycosylated inner-envelope (M) proteins were present on the external surface. In addition, small segments of the viral envelope glycoproteins (HN and F1) were removed by these proteases, while the major portions of the glycoproteins were protected from digestion, indicating that in the erythrocyte membrane they are transmembrane proteins. Results of experiments carried out on right side-out membranes, unsealed membranes, and membranes containing attached virus that was unable to fuse indicated that the results obtained with IO membranes could not be accounted for by contamination with these membrane species. The identify of the proteolysis products was confirmed by peptide mapping. The selective exposure of the cytoplasmic surface, and hence the internal components of the virus, in IO vesicles makes this membrane system an attractive model for studying the interactions involved in virus maturation at host cell membranes.
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PMID:Glycoproteins of Sendai virus are transmembrane proteins. 23 Apr 85

Young rats treated with 10 to 14 daily injections of 2,4-dichlorophenoxyacetate (2,4-D) developed a myopathy mainly involving fast muscles. Myosin isolated from the gastrocnemius muscles of treated and normal control animals differed in several respects. The Ca2+- and Mg2+-mediated ATPases were higher in myopathic muscle myosin than in normals. Alkylation of thiols by N-ethylmaleimide (NEM) induced an increase of Ca2+-activated ATPase that was higher in normal than in myopathic myosin. Trinitrophenylation of reactive amino groups by 2,4,6-trinitrobenzene sulfonate (TBS) induced on increase in Mg2+-mediated ATPase in both preparations, but the increase was higher in normals. Although the heavy- and light-chain pattern was identical in normal and myopathic myosin, during storage at 0 degrees C the relative amount of myopathic L2 light chain decreased. Myosins fragmented either by limited proteolysis with trypsin and chymotrypsin or by specific cleavage at tryptophanyl and cysteinyl peptide bonds showed differences on sodium dodecylsulfate (SDS)-polyacrylamide-gel electrophoresis. The results indicate that there is a change in the heavy chains of myosin isolated from the gastrocnemius muscle in 2,4-D-induced rat myopathy.
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PMID:Myosin changes in experimental 2,4-dichlorophenoxyacetate myopathy. 23 48

In vitro studies revealed that the hatching of oncospheres of Moniezia expansa requires the mechanical breakage of the eggshell and subshell membrane and enzymic digestion of the pyriform apparatus. Removal of the outer two egg membranes elicits the activation of most oncospheres. Between pH 5.0-7.8, there is no significant difference in numbers of oncospheres activated by eggshell removal and the addition of sodium bicarbonate has no effect. Solutions of more extreme pH values (2.0 and 10.0) are harmful and render oncospheres immobile. The subshell membrane forms a barrier to the passage of water in an osmotic gradient and to several molecular and ionic substances. Between the eggshell and subshell membrane is a layer of droplets which have a strong affinity for Sudan stains and which are partially removed by lipase. The eggshell is resistant to a variety of proteolytic enzymes, amylases and lipase. The pyriform apparatus is digested by chymotrypsin and pepsin, though not by trypsin. Both eggshell and pyriform apparatus are dissolved by solutions of sodium sulphide and sodium hypochlorite, indicating that their structures are stabilized by disulphide bonds and other covalent linkages.
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PMID:In vitro hatching of the tapeworm Moniezia expansa (Cestoda: Anoplocephalidae) and some properties of the egg membranes. 23 60


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