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 94-kDa glucose-regulated protein (endoplasmin, grp94) is an abundant member of the 90-kDa molecular chaperone family in the endoplasmic reticulum. We have found earlier that the 50% homologous 90-kDa heat shock protein, hsp90, has ATP-binding site(s) and autophosphorylating activity (Csermely, P., and Kahn, C. R. (1991) J. Biol. Chem. 266, 4943-4950). In the present paper we demonstrate that highly purified grp94 is also able to autophosphorylate itself on serine and threonine residues. grp94 can be freed from the co-purifying casein kinase II by concanavalin A affinity chromatography, and its phosphorylation is unaffected by activators and inhibitors of numerous protein kinases known to associate with the homologous hsp90. The autophosphorylation persists in immunoprecipitates and in SDS-polyacrylamide gel-purified and renatured grp94. Autophosphorylation displays a monomolecular kinetics, is activated by micromolar calcium concentrations, has an extreme heat stability, and can utilize both ATP and GTP with relatively high km values of 243 +/- 14 microM and 116 +/- 23 microM, respectively. Sequence analysis of grp94 shows the presence of two ATP-binding sites. The major product of limited proteolysis of grp94 by chymotrypsin or papain is an N-terminal 85-kDa fragment that can bind to ATP-agarose but does not show autophosphorylation. Our data suggest that grp94 has an enzymatic function analogous in many respects to the similar activity of hsp70, hsp90, and grp78 (BiP). Autophosphorylation may participate in/regulate the complex formation of these proteins, so it may be involved in their chaperone function.
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PMID:Autophosphorylation of grp94 (endoplasmin). 789 Jul 76

Bovine lactoferrin binds to a 60 kDa heat shock protein of Helicobacter pylori. Binding ability was related to human immunoglobulin G because bovine lactoferrin binding proteins were isolated by extraction of cell surface associated proteins with distilled water, applied on IgG-Sepharose and nickel sulphate chelate affinity chromatography. Binding was demonstrated by Western blot after purified protein was digested with alpha-chymotrypsin and incubated with peroxidase-labeled bovine lactoferrin. Binding was inhibited by bovine lactoferrin, lactose, rhamnose, galactose, and two iron-containing proteins, ferritin and haptoglobin. Helicobacter pylori binds ferritin and haptoglobin via charge or hydrophobic interactions because this binding was not inhibited by specific and various glycoproteins or carbohydrates. Carbohydrate moieties of bovine lactoferrin molecules seem to be involved in binding because glycoproteins with similar carbohydrate structures strongly inhibited binding. Scatchard plot analysis of the binding of peroxidase-labeled bovine lactoferrin to H. pylori cells yielded a kd 2.88 x 10(-6) M. In addition, binding of H. pylori cells to bovine lactoferrin was enhanced when bacteria treated with pepsin or alpha-chymotrypsin after isolation from iron-restricted and iron-containing media.
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PMID:Cryptic domains of a 60 kDa heat shock protein of Helicobacter pylori bound to bovine lactoferrin. 911 43

Mycobacterium tuberculosis heat shock protein 16.3 (MTB HSP 16.3) accumulates as the dominant protein in the latent stationary phase of tuberculosis infection. MTB HSP 16.3 displays several characteristics of small heat shock proteins (sHsps): its expression is increased in response to stress, it protects against protein aggregation in vitro, and it contains the core 'alpha-crystallin' domain found in all sHsps. In this study we characterized the chaperone activity of recombinant MTB HSP 16.3 in several different assays and compared the results to those obtained with recombinant human alphaB-crystallin, a well characterized member of the sHsp family. Recombinant MTB HSP 16.3 was expressed in Escherichia coli and purified to apparent homogeneity. Similar to alphaB-crystallin, MTB HSP16.3 suppressed citrate synthase aggregation and in the presence of 3.5 mm ATP the chaperone activity was enhanced by twofold. ATP stabilized MTB HSP 16.3 against proteolysis by chymotrypsin, and no effect was observed with ATPgammaS, a nonhydrolyzable analog of ATP. Increased expression of MTB HSP 16.3 resulted in protection against thermal killing in E. coli at 48 degrees C. While the sequence similarity between human alphaB-crystallin and MTB HSP 16.3 is only 18%, these results suggest that the functional similarities between these proteins containing the core 'alpha-crystallin' domain are much closer.
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PMID:Functional similarities between the small heat shock proteins Mycobacterium tuberculosis HSP 16.3 and human alphaB-crystallin. 1195 82