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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Streptomyces griseus trypsin (SGT) is a bacterial serine proteinase that is more homologous to mammalian than to other bacterial enzymes. The structure of SGT has been solved primarily by molecular replacement, though some low-resolution phase information was supplied by heavy-atom derivatives. The mammalian pancreatic serine proteinases bovine trypsin (BT) and alpha-chymotrypsin (CHT) were used as molecular replacement models. Because these proteins have low homology with SGT compared to the majority of other successful replacement models, new strategies were required for molecular replacement to succeed. The model of SGT has been refined at 1.7 A resolution to a final R-factor of 0.161 (1 A = 0.1 nm); the correlation coefficient between all observed and calculated structure factor amplitudes is 0.908. Solvent molecules located in the crystal structure play an important role in stabilizing buried charged and polar groups. An additional contribution to stability can be seen in the fact that the majority of the charged side-chains are involved in ionic interactions, sometimes linking the two domains of SGT. A comparison of SGT with BT shows that the greatest similarities are in the active-site and substrate-binding regions, consistent with their similar substrate specificities. The modeling of complexes of SGT with two inhibitors of BT, pancreatic trypsin inhibitor (PTI) and the third domain of Japanese quail ovomucoid (OMJPQ3), helps to explain why PTI inhibits SGT but OMJPQ3 does not. Like BT, but unlike other bacterial serine proteinases of known structure, SGT has a buried N terminus. SGT has also a well-defined Ca2+-binding site, but this site differs in location from that of BT.
J Mol Biol 1988 Apr 05
PMID:Refined crystal structure of Streptomyces griseus trypsin at 1.7 A resolution. 313 12

Plasminogen Activator (PA) and its response to glucocorticoids and androgens was studied in viable rat thymocytes in suspension. PA was measured by its ability to convert plasminogen to plasmin, and the formed plasmin determined by cleavage of 14C-labeled globin. Using this functional assay, PA was found to be associated with the outer surface of thymic cells, and only negligible activity recovered from the incubation medium. Rat thymocytes also contain cytoplasmic and nuclear inhibitor(s) of the serine proteases plasmin, trypsin, chymotrypsin and thymic PA. Release of these inhibitors prevented determination of thymic PA activity in presence of lysed cells. The specific activity of PA in thymocytes isolated from adrenalectomized-castrated rats did not differ significantly from the specific activity associated with cells from intact animals. Furthermore, treatment of adrenalectomized-castrated rats with 0.1 mg of dexamethasone/kg for 2 days induced thymic involution without affecting thymic PA activity. These observations suggest that PA activity of thymocytes is not involved in glucocorticoid-mediated thymic involution.
Mol Cell Biochem 1985 Mar
PMID:Plasminogen activator and protease inhibitor activities in isolated rat thymocytes. 315 48

Using limited chymotrypsin and trypsin digestion of isolated Physarum histone H1 labeled in vivo in postsynthetically added N epsilon-methyl groups of lysine we show that: --there is no postsynthetic methylation in the central globular domain of H1, --a moderate number of methylated sites occurs in the N-terminal fragment and the part of the C-terminal fragment directly adjacent to the globular domain (the main site of interphase phosphorylation), --the most intensively methylated region occurs within the sequence located in an extended part of the C-terminal fragment, distant to the globular domain and the main site of interphase phosphorylation.
Mol Biol Rep 1988
PMID:Distribution of postsynthetic methylation sites in Physarum histone H1. 322 47

Mast cell proteinases are known to be released in response to helminth infection, and are, in particular, characteristic of the immune rejection of intestinal nematode parasites. In intestinal mucosal tissue the relevant enzyme is rat mast cell proteinase II (RMCP II) and that of other tissues, including the lung, is rat mast cell proteinase I (RMCP I). The function of these enzymes is unknown, and we have examined the possibility that they directly attack the parasites. This was done by examining the cleavage patterns produced by both proteinases on 125I-labelled excretory/secretory (ES) products of two intestinal nematodes (the infective larva of Ascaris suum, and adult Nippostrongylus brasiliensis) and one which has a pulmonary migration route (the third/fourth stage larva of A. suum). It was first established that all the labelled molecules were proteinaceous, by their susceptibility to broad spectrum proteinases, and that none were host components carried over into culture, by their antigenicity to infected hosts. All the nematode ES products were found to be remarkably resistant to RMCP I and II, only one major component of the infective larva of A. suum being cleaved by both enzymes. This was not found to reflect a resistance to serine proteinases in general, since selected ES components were cleaved by chymotrypsin and trypsin. This would, therefore, argue that, if the enzymes play any direct role in the immune expulsion of nematodes, it is unlikely to be successfully directed at their secretions.
Mol Biochem Parasitol 1987 Jun
PMID:Resistance of nematode secretory products to cleavage by mast cell proteinases. 330 71

The thiol-specific photoactivatable reagent 4-(2-iodoacetamido)benzophenone (BPIA) can be selectively incorporated into the SH-1 of myosin subfragment 1 (S1), and upon photolysis an intramolecular cross-link is formed between SH-1 and the N-terminal 25-kDa region of S1. If a Mg2+-nucleotide is present during photolysis, cross-links can be formed either with the 25-kDa or with the central 50-kDa region [Lu, R. C., Moo, L., & Wong, A. G. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 6392-6396]. Heavy chains with these two types of intramolecular cross-links and un-cross-linked heavy chain have different mobility on sodium dodecyl sulfate (NaDodSO4)-polyacrylamide gels and therefore can be purified electrophoretically. Each type of heavy chain was cleaved with Staphylococcus aureus protease, chymotrypsin, or lysyl endopeptidase. The cleavage points were determined on the basis of the molecular weights of weights of peptides containing the N-terminus, which was identified with the use of an antibody. Locations of the cross-links were deduced by comparing the peptide maps of cross-linked and un-cross-linked heavy chains. The results indicate that the segment located about 12-16 kDa from the N-terminus of the heavy chain can be cross-linked to SH-1 via BPIA independently of the presence of a nucleotide, whereas the segment located 57-60 kDa from the N-terminus can be cross-linked to SH-1 only in the presence of a Mg2+-nucleotide. With use of the avidin-biotin system, it has been shown that SH-1 is located 13 nm from the head/rod junction [Sutoh, K., Yamamoto, K., & Wakabayashi, T. (1984) J. Mol. Biol. 178, 323-339]. Since BPIA spans less than 1 nm, our results show that two regions, separated by approximately 400 amino acid residues and located in the 25- and 50-kDa domains of S1, respectively, are also part of the head structure about 12-14 nm from the head/rod junction.
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PMID:Identification of two segments, separated by approximately 45 kilodaltons, of the myosin subfragment 1 heavy chain that can be cross-linked to the SH-1 thiol. 331 Nov 49

We investigated the binding of C4 and C3 to red cell surfaces by non-complement enzymes. Cell bound C components were quantitated by a radioimmunoassay, the chain structure of bound components was analyzed by Western blotting and the hemolytic activity of bound components was determined. Trypsin, chymotrypsin, plasmin, elastase, thrombin, kallikrein and enzymes from Bacillus subtilis, Staphylococcus aureus and Streptomyces griseus all were found capable of binding C4b and C3b to sheep red cells. C4b bound by any of these enzymes was hemolytically active; both classical and alternate pathway activity of C3 could be demonstrated for most enzymes except plasmin and thrombin. In addition, trypsin and the bacterial enzymes were also able to generate the classical pathway C3-convertase from C4b + C2. The hemolytic efficiency of enzyme bound C4b and C3b was about the same as for these molecules bound by complement enzymes. In contrast, the process of binding by the non-complement enzymes was several hundred-fold less efficient than by cell bound complement enzymes. The results demonstrate that several enzymes can replace the C1 and C42 enzymes in the classical pathway and are able to initiate the alternative pathway by activating C3 and binding C3b to the cell surface.
Mol Immunol 1988 May
PMID:Binding and activation of C4 and C3 on the red cell surface by non-complement enzymes. 341 32

The molecular structure of the complex between bovine pancreatic alpha-chymotrypsin (EC 3.4.4.5) and the third domain of the Kazal-type ovomucoid from Turkey (OMTKY3) has been determined crystallographically by the molecular replacement method. Restrained-parameter least-squares refinement of the molecular model of the complex has led to a conventional agreement factor R of 0.168 for the 19,466 reflections in the 1.8 A (1 A = 0.1 nm) resolution shell [I greater than or equal to sigma (I)]. The reactive site loop of OMTKY3, from Lys13I to Arg21I (I indicates inhibitor), is highly complementary to the surface of alpha-chymotrypsin in the complex. A total of 13 residues on the inhibitor make 113 contacts of less than 4.0 A with 21 residues of the enzyme. A short contact (2.95 A) from O gamma of Ser195 to the carbonyl-carbon atom of the scissile bond between Leu18I and Glu19I is present; in spite of it, this peptide remains planar and undistorted. Analysis of the interactions of the inhibitor with chymotrypsin explains the enhanced specificity that chymotrypsin has for P'3 arginine residues. There is a water-mediated ion pair between the guanidinium group on this residue and the carboxylate of Asp64. Comparison of the structure of the alpha-chymotrypsin portion of this complex with the several structures of alpha and gamma-chymotrypsin in the uncomplexed form shows a high degree of structural equivalence (root-mean-square deviation of the 234 common alpha-carbon atoms averages 0.38 A). Significant differences occur mainly in two regions Lys36 to Phe39 and Ser75 to Lys79. Among the 21 residues that are in contact with the ovomucoid domain, only Phe39 and Tyr146 change their conformations significantly as a result of forming the complex. Comparison of the structure of the OMTKY3 domain in this complex to that of the same inhibitor bound to a serine proteinase from Streptomyces griseus (SGPB) shows a central core of 44 amino acids (the central alpha-helix and flanking small 3-stranded beta-sheet) that have alpha-carbon atoms fitting to within 1.0 A (root-mean-square deviation of 0.45 A) whereas the residues of the reactive-site loop differ in position by up to 1.9 A (C alpha of Leu18I). The ovomucoid domain has a built-in conformational flexibility that allows it to adapt to the active sites of different enzymes. A comparison of the SGPB and alpha-chymotrypsin molecules is made and the water molecules bound at the inhibitor-enzyme interface in both complexes are analysed for similarities and differences.
J Mol Biol 1987 May 20
PMID:Crystal and molecular structures of the complex of alpha-chymotrypsin with its inhibitor turkey ovomucoid third domain at 1.8 A resolution. 347 45

Three monoclonal antibodies (mAbs), termed SN2, SN2a and SN2b, were used in the present work to study a human T-cell leukemia-associated cell surface glycoprotein, GP37. Strong specificity of mAbs SN2, SN2a and SN2b for T leukemia cells was demonstrated by radioimmunoassay and fluorescence-activated cell sorter (FACS) analysis. GP37 was not detected on normal human peripheral blood lymphocytes, purified normal T-cells, normal thymocytes nor normal bone marrow cells. Furthermore, GP37 was barely detectable on phytohemagglutinin (PHA)- and Concanavalin A (Con A)-activated T-cells. The results indicate clinical utility of these mAbs. Competitive binding experiments show that the epitopes recognized by SN2 and SN2a are sufficiently close to each other to allow complete reciprocal inhibition of binding whereas the epitopes recognized by SN2 and SN2b are less close to allow only partial reciprocal binding inhibition. The biochemical nature of antigenic determinants defined by these mAbs was studied by treating T leukemia cells with trypsin, chymotrypsin, thermolysin, neuraminidase and mixed glycosidases. The results suggest that the antigenic determinants defined by these mAbs all consist of the protein moiety of the glycoprotein GP37. No significant antigenic modulation was observed when T leukemia cells were reacted with SN2. In a sequential immunoprecipitation experiment, a 125I-labeled leukemia antigen preparation was first treated with a rabbit anti-T leukemia antiserum. The latter had been prepared by immunizing a rabbit with a partially purified human T leukemia antigen preparation and showed a good specificity for T leukemia cells. Subsequent treatment of the labeled antigen preparation with SN2 showed that SN2 antigen had been precleared. Thus, both mouse mAb SN2 and the rabbit anti-T leukemia antiserum react with the same GP37 molecule.
Mol Immunol 1986 Jun
PMID:Human T-cell leukemia-associated cell surface glycoprotein GP37: studies with three monoclonal antibodies and a rabbit antiserum. 348 64

Local melting within the subfragment-2 region of activated rabbit skeletal glycerinated muscle fibers has been investigated over the temperature range 5 to 37 degrees C, using an enzyme (chymotrypsin)-probe method. The cleavage rates were determined from the time-course of formation of digestion products by electrophoresis on sodium dodecyl sulfate-containing polyacrylamide gels. We found the cleavage sites to be localized in a restricted region Mr = 64,000 to 90,000/polypeptide chain, measured from the C terminus of the myosin rod (the subfragment-2 hinge domain). The cleavage rate constant for activated muscle fibers in the presence of an ATP-regenerating system was about 100 times larger at each temperature than that for rigor or for relaxed muscle fibers and showed a marked increase in magnitude with increasing temperature. Comparative plots of the apparent rate-constant for cleavage within the subfragment-2 hinge domain and the isometric force generated by active fibers versus MgATP concentration gave closely similar profiles suggesting a strong positive correlation. Thus, there appears to be a close coupling between the conformational transition within the subfragment-2 hinge domain and contractile force when the cross-bridges undergo cycling.
J Mol Biol 1986 Jul 05
PMID:Local melting in the subfragment-2 region of myosin in activated muscle and its correlation with contractile force. 349 Dec 13

The complete amino acid sequence of H-protein from chicken liver was determined by aligning peptides obtained by cyanogen bromide, endoproteinase Lys-C, Staphylococcus aureus V8 protease, and chymotrypsin cleavage together with the partial NH2- and COOH-terminal sequence of the intact protein. H-protein consists of 125 amino acids and a lipoic acid moiety linked to lysine 59. The sequence is: (sequence in text). The lysyl residue involved in lipoic acid attachment is indicated with an asterisk. The molecular weight including lipoic acid is calculated to be 13,883. From the secondary structure predicted by the method of Chou and Fasman (Chou, P. Y., and Fasman, G. D. (1978) Adv. Enzymol. 47, 45-148) the lipoic acid binding region shows alpha-helical structure and is predicted to be an interior portion of the protein from the hydropathic profile according to Kyte and Doolittle (Kyte, J., and Doolittle, R. F. (1982) J. Mol. Biol. 157, 105-132).
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PMID:Chicken liver H-protein, a component of the glycine cleavage system. Amino acid sequence and identification of the N epsilon-lipoyllysine residue. 352 81


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