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: CAS:61-90-5 (leucine)
60,841 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The purpose of these experiments was to study the physical structure of the nucleocapsid-M protein complex of vesicular stomatitis virus by analysis of nucleocapsid binding by wild-type and mutant M proteins and by limited proteolysis. We used the temperature-sensitive M protein mutant tsO23 and six temperature-stable revertants of tsO23 to test the effect of sequence changes on M protein binding to the nucleocapsid as a function of NaCl concentration. The results showed that M proteins from wild-type, mutant, and three of the revertant viruses had similar NaCl titration curves, while the curve for M proteins from the other three revertants differed significantly. The altered NaCl dependence of M protein was correlated with a single amino acid substitution from Phe to Leu at position 111 compared with the original temperature-sensitive mutant and was not correlated with a substitution of Gly to Glu at position 21 in tsO23 and the revertants. To determine whether protease cleavage sites in the M protein were protected by interaction with the nucleocapsid, nucleocapsid-M protein complexes were subjected to limited proteolysis with trypsin, chymotrypsin, or Staphylococcus aureus V8 protease. The initial trypsin and chymotrypsin cleavage sites, located after amino acids 19 and 20, respectively, were as accessible to proteases when M protein was bound to the nucleocapsid as when it was purified, indicating that this region of the protein does not interact directly with the nucleocapsid. Furthermore, trypsin or chymotrypsin treatment released the M protein fragments from the nucleocapsid, presumably due to conformational changes following proteolysis. V8 protease cleaved the M protein at position 34 or 50, producing two distinct fragments. The M protein fragment produced by V8 protease cleavage at position 34 remained associated with the nucleocapsid, while the fragment produced by cleavage at position 50 was released from the nucleocapsid. These results suggest that the amino-terminal region of the M protein around amino acid 20 does not interact directly with the nucleocapsid and that conformational changes resulting from single-amino-acid substitutions at other sites in the M protein are important for this interaction.
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PMID:Sequences of the vesicular stomatitis virus matrix protein involved in binding to nucleocapsids. 184 35

Reactive oxygen intermediates and serine proteases are important components of host defense systems but can produce host injury if not tightly regulated. To determine whether these components can be coordinately controlled, we investigated regulation of superoxide generation by physiologically relevant concentrations of a) highly purified serum-derived antichymotrypsin (ACT), b) recombinant, wild-type ACT, c) rACT in which amino acid substitutions were engineered into the reactive center, and d) chymotrypsin/ACT complexes. These proteins and protein complexes inhibited superoxide anion production in neutrophils stimulated by f-Met-Leu-Phe, Con A, or PMA. In contrast, ligand-stimulated degranulation was not inhibited. In addition, using the recombinants and complexes, the region of ACT involved in inhibiting superoxide anion production was shown to be structurally distinct from the reactive center of the protein. The results indicate that functional domains of ACT corresponding to different biological activities can be decoupled and suggest that three species of ACT (intact ACT, a complexed protease/ACT form, and a partially denatured or proteolyzed form of ACT) that can exist in the microenvironment of an activated neutrophil may play an important role in regulating neutrophil function.
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PMID:Inhibition of human neutrophil superoxide generation by alpha 1-antichymotrypsin. 184 82

The egg jelly-induced acrosome reaction of the sea urchin, Strongylocentrotus intermedius, was inhibited by succinyl-Leu-Leu-Val-Tyr-4-methyl-coumaryl-7-amide (Suc-Leu-Leu-Val-Tyr-MCA), but not by Suc-Ala-Ala-Pro-Phe-MCA. The proteases with hydrolytic activity toward the former were purified from sperm extract by DEAE-Sephacel and hydroxylapatite chromatographies, Sephacryl S-300 gel filtration, and heparin-Sepharose CL-6B chromatography. Two types of protease were separated, and the molecular weights were estimated to be 65 and 700 kDa, respectively, by gel filtration. The former was accompanied by hydrolytic activity toward Suc-Ala-Ala-Pro-Phe-MCA, which was not hydrolyzed by the latter. Polyacrylamide gel electrophoresis of 700 kDa protease gave a single protein band under nondenaturing conditions and at least eight bands in the range of 22-33 kDa in the presence of sodium dodecyl sulfate (SDS). The substrate specificity and the inhibitor sensitivity of 700 kDa protease indicate that it contains two types of the activity, one is chymotrypsin-type and the other trypsin-type. The former activity was enhanced by poly-L-lysine or SDS. These properties of 700 kDa protease are similar to those of proteasomes (multicatalytic proteinases) isolated from various eukaryotic sources. We had previously shown that inhibitors of chymotrypsin-like proteases inhibit the increase of intracellular Ca2+ concentration by egg jelly, resulting in the inhibition of the acrosome reaction of St. intermedius (Matsumura and Aketa, Gamete Res 23:255-266, 1989). Bringing these findings together, we suggest that the chymotrypsin-like activity of sperm proteasome participates in the onset of the acrosome reaction of St. intermedius.
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PMID:Proteasome (multicatalytic proteinase) of sea urchin sperm and its possible participation in the acrosome reaction. 187 26

A metallo-endopeptidase, which appears to be an integral membrane protein of rat kidney, was purified to homogeneity by a series of standard chromatographic procedures. This enzyme significantly hydrolyzed human parathyroid hormone [hPTH(1-84)] and a synthetic substrate Suc-Leu-Leu-Val-Tyr-Mec (Suc = succinyl, Mec = 4-methyl-coumarinyl-7-amide). The purified enzyme had apparent molecular masses of 250 kDa on gel filtration, and 88 kDa and 245 kDa on sodium dodecyl sulfate/polyacrylamide gel electrophoresis under reducing and non-reducing conditions, respectively. Its pH optimum for activity was 8.0-8.5 and its isoelectric point was pH 4.9. Its activity was inhibited by EDTA, EGTA and o-phenanthroline, but not by phosphoramidon. The metal-depleted enzyme was reactivated by the addition of metal ions. The enzyme was also inhibited by chymostatin and eglin C, and by thiol compounds. Of the synthetic substrates examined, the enzyme hydrolyzed only Suc-Leu-Leu-Val-Tyr-Mec, one of the synthetic substrates for alpha-chymotrypsin. It did not hydrolyze synthetic substrates with less than four amino acid residues with tyrosine in the P1 position. The enzyme hydrolyzed hPTH and reduced hen egg lysozyme but did not hydrolyze azocasein or [3H]methyl-casein. NH2-terminal amino acid sequence analyses of the degradation products of hPTH(1-84) and reduced hen egg lysozyme by the purified enzyme revealed that the enzyme preferentially cleaved these peptides at peptide bonds flanked by hydrophilic amino acid residues. Amino acid analyses showed that the main degradation products of PTH were hPTH(17-29), hPTH(30-38) and hPTH(74-84). The ability of the enzyme to hydrolyze peptide bonds flanked by hydrophilic amino acid residues and its inability to degrade azocasein distinguish it from several other kidney endopeptidases reported, such as endopeptidase 24.11 and meprin.
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PMID:A membrane-bound metallo-endopeptidase from rat kidney hydrolyzing parathyroid hormone. Purification and characterization. 188 19

It has been shown that the P1 site (the center of the reactive site) of protease inhibitors corresponds to the specificity of the cognate protease, and consequently specificity of Streptomyces subtilisin inhibitor (SSI) can be altered by substitution of a single amino acid at the P1 site. In this paper, to investigate whether similar correlation between inhibitory activity of mutated SSI and substrate preference of protease is observed for subtilisin BPN', which has broad substrate specificity, a complete set of mutants of SSI at the reaction site P1 (position 73) was constructed by cassette and site-directed mutagenesis and their inhibitory activities toward subtilisin BPN' were measured. Mutated SSIs which have a polar (Ser, Thr, Gln, Asn), basic (Lys, Arg), or aromatic amino acid (Tyr, Phe, Trp, His), or Ala or Leu, at the P1 site showed almost the same strong inhibitory activity toward subtilisin as the wild type (Met) SSI. However, the inhibitory activity of SSI variants with an acidic (Glu, Asp), or a beta-branched aliphatic amino acid (Val, Ile), or Gly or Pro, at P1 was decreased. The values of the inhibitor constant (Ki) of mutated SSIs toward subtilisin BPN' were consistent with the substrate preference of subtilisin BPN'. A linear correlation was observed between log(1/Ki) of mutated SSIs and log(1/Km) of synthetic substrates. These results demonstrate that the inhibitory activities of P1 site mutants of SSI are linearly related to the substrate preference of subtilisin BPN', and indicate that the binding mode of the inhibitors with the protease may be similar to that of substrates, as in the case of trypsin and chymotrypsin.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Inhibition of subtilisin BPN' by reaction site P1 mutants of Streptomyces subtilisin inhibitor. 190 59

A principal neutralizing domain (PND) of the major envelope glycoprotein (gp120) of the HTLV-III BH10 strain of human immunodeficiency virus type 1 (HIV-1) has significant amino acid similarities to a reactive site of Kunitz-type basic proteinase inhibitors. We therefore thought that the PND may interact with cellular proteinase-like molecule(s) upon HIV-1 infection and measured the cellular proteolytic activities at the surface of intact Molt-4 clone 8 cells, which are highly susceptible to HIV-1 infection. The cells preferentially cleaved succinyl-Leu-Leu-Val-Tyr-4-methylcoumaryl-7-amide, a good substrate of chymotrypsin, and the activity was strongly inhibited by N-tosyl-L-phenylalanyl chloromethyl ketone (IC50 = 11.5 microM) and chymostatin (IC50 = 4.8 microM). A synthetic peptide of 24 residues (amino acids 308-331) that correspond to the PND also inhibited the cellular proteolytic activity in a dose-dependent manner (IC50 = 79.2 microM). The inhibition was still observed at low temperature (IC50 = 42.7 microM) and even after the peptide-treated cells were washed. We therefore think that the peptide interacts with proteinase-like molecule(s) located at the surface of the cells. The synthetic peptides from four other strains of HIV-1 corresponding to the PND similarly inhibited the proteolytic activity. These results may be helpful to clarify the novel mechanism(s) for HIV-1 infection.
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PMID:A principal neutralizing domain of human immunodeficiency virus type 1 interacts with proteinase-like molecule(s) at the surface of Molt-4 clone 8 cells. 191 51

Heparin cofactor II (HCII) is a glycoprotein in human plasma that inhibits thrombin and chymotrypsin. Inhibition occurs when the protease attacks the reactive site peptide bond in HCII (Leu444-Ser445) and becomes trapped as a covalent 1:1 complex. Dermatan sulfate and heparin increase the rate of inhibition of thrombin, but not of chymotrypsin, greater than 1000-fold. The N-terminal portion of HCII contains two acidic repeats (Glu56-Asp-Asp-Asp-Tyr-Leu-Asp and Glu69-Asp-Asp-Asp-Tyr-Ile-Asp) that may bind to anion-binding exosite I of thrombin to facilitate covalent complex formation. To examine the importance of the acidic domain, we have constructed a series of 5' deletions in the HCII cDNA and expressed the recombinant HCII (rHCII) in Escherichia coli. Apparent second-order rate constants (k2) for inhibition of alpha-thrombin and chymotrypsin by each variant were determined. Deletion of amino acid residues 1-74 had no effect on the rate of inhibition of alpha-thrombin or chymotrypsin in the absence of a glycosaminoglycan. Similarly, the rate of inhibition of alpha-thrombin in the presence of a glycosaminoglycan was unaffected by deletion of residues 1-52. However, deletion of residues 1-67 (first acidic repeat) or 1-74 (first and second acidic repeats) greatly decreased the rate of inhibition of alpha-thrombin in the presence of heparin, dermatan sulfate, or a dermatan sulfate hexasaccharide that comprises the minimum high-affinity binding site for HCII. Deletion of one or both of the acidic repeats increased the apparent affinity of rHCII for heparin-Sepharose, suggesting that the acidic domain may interact with the glycosaminoglycan-binding site of native rHCII. The stimulatory effect of glycosaminoglycans on native rHCII was decreased by a C-terminal hirudin peptide which binds to anion-binding exosite I of alpha-thrombin. Furthermore, the ability of native rHCII to inhibit gamma-thrombin, which lacks the binding site for hirudin, was stimulated weakly by glycosaminoglycans. These results support a model in which the stimulatory effect of glycosaminoglycans on the inhibition of alpha-thrombin is mediated, in part, by the N-terminal acidic domain of HCII.
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PMID:The N-terminal acidic domain of heparin cofactor II mediates the inhibition of alpha-thrombin in the presence of glycosaminoglycans. 193 83

Nucleosome cores were digested with alpha-chymotrypsin until histone H3 was degraded to a partial histone, CP1. As we reported previously, cleavage occurred at leucine 20 to H3 and resulted in an increase in circular dichroism between 265 to 285 nm. Some modest core unfolding was also observed as determined by a small decrease in the sedimentation coefficient. Studies reported here deal with the analysis of core secondary structure and subsequent perturbation caused by treatment with alpha-chymotrypsin. Raman spectroscopy indicated that chymotryptic treatment promoted a change in the conformational environment of a population of core histone tyrosines. In addition, a shift from B-form to an intermediate B- or A-form was observed for core DNA. High-resolution thermal denaturation was used to determine alterations in the stabilization of core DNA related to perturbation of the core histones. Brief chymotryptic treatment indicated changes in both pre-melt and irreversible transitions.
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PMID:Probing nucleosome core secondary structure before and after alpha-chymotrypsin treatment by Raman spectroscopy and thermal denaturation. 193 63

Incorporation of beta-alanine or gamma-aminobutyric acid in position P2 of ACHPA or Leu psi [CHOHCH2]Val-based tetrapeptides gave highly active renin inhibitors (compounds V, VI, and XVII) with high specificity for renin and a remarkable stability against chymotrypsin. Replacement of the amide bond between P2 and P3 by isosteres (ketomethylenes, hydroxyethylenes, and the corresponding thio-insertion analogues) led to compounds (VIII-XIII, XVIII, and XIX) with renin inhibitory activity in the nanomolar range. Oral activity was achieved by incorporation of polar functionalities at the N-terminus of beta-alanine-containing tetrapeptides. One of these compounds (XXVIII) was chosen for further studies. This inhibitor demonstrated excellent efficacy and a long duration of action after intravenous and oral administration to cynomolgus monkeys.
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PMID:Substrate analogue renin inhibitors containing replacements of histidine in P2 or isosteres of the amide bond between P3 and P2 sites. 195 45

The reactive sites and the C-terminal sequences of three trypsin chymotrypsin inhibitors from fenugreek seeds (TFI-B2, TFI-N2, and TFI-A8) were determined by chemical modification and carboxypeptidase degradation of native und enzymatically modified inhibitors. TFI-B2 contained lysine and leucine in the trypsin- and chymotrypsin-reactive sites, respectively, and -(Lys)-Phe-Leu-Ile was the C-terminal sequence. TFI-N2 possessed arginine and leucine in the trypsin- and chymotrypsin-reactive sites, respectively, and -(Tyr)-Lys-Ile-Leu at the C-terminus. TFI-A8 contained two arginines, one in each of the two reactive sites. At least one of these sites, although mainly directed against trypsin, could also bind some chymotrypsin. -(Leu)-Phe-Ile-Arg was found to be the C-terminus in TFI-A8. These results confirmed that all three fenugreek inhibitors belong to the Bowman-Birk proteinase inhibitor family.
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PMID:Inhibitors of human and bovine trypsin and chymotrypsin in fenugreek (Trigonella foenum-graecum L.) seeds. Reactive sites and C-terminal sequences. 196 6


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