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:3.4.21.4 (trypsin)
42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Penetration of a cell membrane as an early event in infection of cells by mammalian reoviruses appears to require a particular type of viral particle, the infectious subvirion particle (ISVP), which is generated from an intact virion by proteolytic cleavage of the outer capsid proteins sigma 3 and mu 1/mu 1C. Characterizations of the structural components and properties of ISVPs are thus relevant to attempts to understand the mechanism of penetration by reoviruses. In this study, a novel, approximately 13-kDa carboxy-terminal fragment (given the name phi) was found to be generated from protein mu 1/mu 1C during in vitro treatments of virions with trypsin or chymotrypsin to yield ISVPs. With trypsin treatment, both the carboxy-terminal fragment phi and the amino-terminal fragment mu 1 delta/delta were shown to be generated and to remain attached to ISVPs in stoichiometric quantities. Sites of protease cleavage were identified in the deduced amino acid sequence of mu 1 by determining the amino-terminal sequences of phi proteins: trypsin cleaves between arginine 584 and isoleucine 585, and chymotrypsin cleaves between tyrosine 581 and glycine 582. Findings in this study indicate that sequences in the phi portion of mu 1/mu 1C may participate in the unique functions attributed to ISVPs. Notably, the delta-phi cleavage junction was predicted to be flanked by a pair of long amphipathic alpha-helices. These amphipathic alpha-helices, together with the myristoyl group at the extreme amino terminus of mu 1/mu 1N, are proposed to interact directly with the lipid bilayer of a cell membrane during penetration by mammalian reoviruses.
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PMID:A carboxy-terminal fragment of protein mu 1/mu 1C is present in infectious subvirion particles of mammalian reoviruses and is proposed to have a role in penetration. 132 74

Monoclonal antibodies were raised that specifically recognize the NH2-terminal neoepitope sequence present in link protein cleavage products derived from stromelysin-degraded proteoglycan aggregate. Competitive enzyme-linked immunosorbent assay, using synthetic peptides as inhibitors, showed that one of these antibodies (CH-3) required, for antibody recognition, the free NH2-terminal amino acid isoleucine (residue 17 of the intact protein) in the sequence NH2-IQAENG at the stromelysin cleavage site of link protein 3. Human proteoglycan aggregate was digested with recombinant human stromelysin, bovine chymotrypsin, bovine trypsin, and porcine elastase, and their respective link protein degradation products were tested for immunoreactivity with antibody CH-3. Only stromelysin- and chymotrypsin-generated link protein 3 were recognized by antibody CH-3. Both of these enzymes generate link protein NH2 termini with the sequence 17IQAENG. . .; hence these studies indicated that monoclonal antibody CH-3 recognized this neoepitope sequence in only specific proteolytically modified link protein molecules. Since the occurrence of link protein 3 increases with aging, the incidence of CH-3 epitope in proteoglycans isolated from human knee articular cartilage of individuals of different ages was investigated. The prevalence of CH-3 epitope was found to be highest in newborn and adolescent articular cartilage samples. However, little CH-3 epitope was detected in older adult cartilage, although considerably more link protein 3 was present in these samples. These results suggest that additional proteolytic agents are responsible for the increased occurrence of link protein degradation products with aging.
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PMID:Monoclonal antibodies recognizing protease-generated neoepitopes from cartilage proteoglycan degradation. Application to studies of human link protein cleavage by stromelysin. 137 86

Grapevine fanleaf nepovirus (GFLV) has a bipartite plus-sense RNA genome. Its structural and functional proteins originate from polyprotein maturation by at least one virus-encoded proteinase. Here we describe the cloning of the 24-kDa proteinase cistron located between the virus-linked protein (VPg) and the RNA-dependent RNA polymerase cistron in GFLV RNA1 (nucleotides 3966 to 4622). Proteinase expressed from this clone is able to cleave GFLV polyprotein P2 in order to produce the coat protein and a 66-kDa protein which is further processed to the 38-kDa presumed movement protein. The GFLV 24-kDa proteinase sequence contains sequence similarities with other nepovirus and comovirus proteinases, particularly at the level of the conserved domains corresponding to the hypothetical catalytic triad and to the substrate-binding pocket (amino acids 192 to 200). Site-directed mutagenesis of residues His43, Glu87, and Leu197 abolished proteinase activity. Inactivation of the enzyme is also observed if the catalytic residue Cys179 was substituted by isoleucine, but replacement by a serine at the same position produced a mutant with an activity identical to that of native proteinase. All our data show that GFLV cysteine proteinase presents structure similarities to the proteinases of cowpea mosaic virus and potyviruses but is most closely related to trypsin.
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PMID:Effects of site-directed mutagenesis on the presumed catalytic triad and substrate-binding pocket of grapevine fanleaf nepovirus 24-kDa proteinase. 151 63

Peptides derived from enzymatic digestions (cathepsin D and trypsin) were characterized and amino acid sequences determined by using their LC/MS spectra. A Frit-FAB interface that produces extensive peptide fragmentation and permits amino acid sequencing at the low picomole level is described for a model antigen, Staphylococcus aureus nuclease (Nase), and an enzyme of unknown structure, yeast aminopeptidase B. The amino acid sequences of peptides derived from digestion of Nase with cathepsin D (a relatively nonspecific endoprotease) were readily deduced and have provided insights into the nature of antigen processing. Frit-FAB LC/MS spectra of the Nase peptides contained a sufficient number of fragment ions to conclusively identify peptides with a mass below 2000 Da. Capillary LC/MS provided a means for the separation and identification of these enzymatically derived peptides in a fraction of the time that would have been required by gas-phase Edman sequence analysis. The optimized Frit-FAB experiment was consequently evaluated for the partial characterization of aminopeptidase B recently purified to homogeneity from Saccharomyces cerevisiae. Sequence-specific ions observed in the Frit-FAB mass spectra of these tryptic peptides were identical with those commonly observed in high-energy collision-induced dissociation (CID) spectra and included side-chain fragment ions that differentiated leucine from isoleucine. These fragment ions were used to deduce entire amino acid sequences for several of the tryptic peptides.
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PMID:Optimization of the fragmentation in a frit-fast atom bombardment ion source for the sequencing of peptides at the picomole level. 175 Jun 99

We report identification, biochemical, clinical, and genetic studies of an apparently benign, electrophoretic variant of serum prealbumin (PALB, transthyretin, TTR) in a North American kindred of Swedish ancestry. The variant polypeptide stems from a C to T point mutation in exon 4 which results in methionine instead of threonine at position 119 of the mature molecule. It was discovered incidentally in a girl with classic alpha-1-anti-trypsin (A1AT) deficiency and her father during diagnostic A1AT phenotyping by ISO-DALT high-resolution two-dimensional electrophoresis (2DE). Twelve relatives in the four-generation paternal kindred, including five individuals who were heterozygous for the variant prealbumin, were studied. In each of these five heterozygotes, the variant allele product was equimolar and isoelectric with the normal protein, yet migrated with an apparently lower mass in the SDS-PAGE dimension. The inheritance pattern was consistent with autosomal dominant transmission. Histories and physical examinations showed no evidence of amyloidosis, as has been observed with other variants of prealbumin. Mean values of serum prealbumin and retinol binding protein levels were higher in the carriers as compared to the normal relatives in the family, but the difference was not statistically significant. Thyroid hormone levels and distribution of thyroxine and triiodothyronine among binding proteins in serum were within reference limits. Four members of the lineage had dominant, scalp-restricted keratinaceous cysts, yet only three of these four individuals had the variant. We counseled the family that this is likely a benign variant with regard to amyloidosis-related morbidity or shortened life span, although senile effects cannot be entirely ruled out. The provisional designation assigned to this allele is PALBCHICAGO. The substitution of methionine at position 119, as predicted by the DNA sequence, was confirmed by amino acid sequencing of CNBr and tryptic peptides. This substitution occurs at a CpG dinucleotide that may be a point mutational "hot spot," as has been postulated for the methionine-30 and isoleucine-122 PALB variants. The apparently lower mass of the variant probably results from a more compact conformation in SDS. With the exception of histidine-58, a charge substitution, all other amyloidosis-related prealbumin variant polypeptides had normal mobility in the ISO-DALT 2DE system.
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PMID:Biochemical and clinical characterization of prealbuminCHICAGO: an apparently benign variant of serum prealbumin (transthyretin) discovered with high-resolution two-dimensional electrophoresis. 187 23

A synthetic gene encoding the protein sequence of mature bovine pancreatic trypsin inhibitor (BPTI) has been cloned into a novel E. coli expression vector. After in vitro gene amplification by successive DNA duplications, more than 600 000 mostly inactive inhibitor molecules may be recovered from a single cell. After purification the inhibitory activity can be reconstituted almost completely. The specificity of BPTI for trypsin is abolished by a single amino acid exchange from lysine to isoleucine at position 15. The altered protein is shown to be an efficient inhibitor of human leukocyte elastase.
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PMID:A synthetic operon containing 14 bovine pancreatic trypsin inhibitor genes is expressed in E. coli. 243 25

Vasoactive intestinal peptide (VIP) receptors were solubilized from rat liver using the zwitterionic detergent CHAPS. Optimal conditions of solubilization were obtained with 5 mM CHAPS and 2.5 mg protein/ml. The binding of 125I-VIP to CHAPS extracts was time- and pH-dependent, saturable and reversible. The following order of potency of unlabeled VIP-related peptides for inhibiting 125I-VIP binding was observed: VIP greater than helodermin greater than peptide histidine isoleucine amide (PHI) greater than rat growth hormone releasing factor (rGRF) greater than secretin. This peptide specificity is identical to that of rat liver membrane-bound receptors. VIP binding activity in the CHAPS extract was destroyed by trypsin or dithiothreitol in accordance with the known sensitivity of membrane-bound receptors to these agents. VIP receptors in CHAPS extracts were stable for at least 5 days at 4 degrees C. Scatchard analysis of equilibrium binding data indicated the presence in CHAPS extracts of high (H) and low (L) affinity binding sites with the following characteristics: KdH = 0.27 nM and BmH = 34 fmol/mg protein; KdL = 51 nM and BmL = 1078 fmol/mg protein. The guanine nucleotide GTP inhibited 125I-VIP binding to soluble receptors and enhanced the dissociation of soluble VIP-receptor complexes, suggesting that GTP-binding proteins were functionally associated with VIP receptors in solution. Gel filtration of solubilized VIP receptors on Sephacryl S-300 revealed a single binding component with a Stokes radius of 6.1 nm. It is concluded that active VIP receptors can be extracted from liver membranes by CHAPS. The availability of this CHAPS-soluble, stable and functional receptor from a tissue which can be obtained in large amounts represents a major step toward the purification of VIP receptors.
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PMID:Solubilization of active and stable receptors for vasoactive intestinal peptide from rat liver. 254 70

The purpose of this work was to solubilize vasoactive intestinal peptide (VIP) receptors from rat small intestinal plasma membranes and to analyze the nature and function of its molecular form(s) in a nondenaturing environment. Membranes were incubated with 3 nM 125I-VIP, washed, and treated with 1% Triton X-100. Chromatography on Sephadex G-50 showed that 60% of the extractable radioactivity was eluted with macromolecular components in the void volume. This radioactive material was dramatically reduced when 1 microM unlabeled VIP was present in the incubation medium or when membranes were pretreated with trypsin or dithiothreitol. Macromolecular components that had bound 125I-VIP were further chromatographed on Sephacryl S-300. Two peaks were observed: a major one (80%) and a minor one (20%) with Stokes radii of 5.2 and 3.1 nm, respectively. The labeling of both components was inhibited by unlabeled VIP or peptide with NH2-terminal histidine and COOH-terminal isoleucine amide (a VIP agonist). The presence of GTP (0.1 mM) in the incubation medium of membranes completely abolished the labeling of the 5.2-nm component but did not affect that of the 3.1-nm one. Moreover, GTP induced dissociation of 125I-VIP from the 5.2-nm component isolated by Sephacryl S-300 chromatography. This effect was time dependent and nucleotide specific. In contrast, GTP did not affect the stability of the 3.1-nm component. After cholera toxin catalyzed [32P]ADP-ribosylation of membranes, chromatography of solubilized material on Sephacryl S-300 showed that a peak of 32P radioactivity was coeluted with the 5.2-nm component.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Solubilization and hydrodynamic characterization of guanine nucleotide sensitive vasoactive intestinal peptide-receptor complexes from rat intestine. 254 61

We report a simple three-step method of generating a homogeneous toxic fragment (toxin) in high yield from B. thuringiensis var. kurstaki. Purified crystals were digested with trypsin at pH 10.5, followed by (NH4)2SO4 precipitation and dialysis. For the HD73 strain the preparation is toxic to eastern-spruce-budworm (Choristoneura fuminiferana) larvae. It gives a single 66 kDa band on polyacrylamide-gel electrophoresis and a single band with an isoelectric point of 5.5 on an isoelectric-focusing gel. A single isoleucine N-terminus was detected, and the first 20 amino acids were found to be identical with those predicted from the gene nucleotide sequence. A single lysine C-terminus was detected, and the amino acid composition was in excellent agreement with tryptic cleavages at arginine-28 and lysine-623 of the protoxin. Raman spectroscopic analysis gave values of 20% alpha-helix, 35% beta-sheet and 45% unordered structure. The resistance of the toxin to most proteinases and its susceptibility to proteolysis by papain and Pronases indicates a compact multidomain structure.
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PMID:Facile preparation and characterization of the toxin from Bacillus thuringiensis var. kurstaki. 254 61

The replication of Moloney murine leukemia virus (MMuLV) in chronically infected mouse cells arrested at the G0/G1 phase of the cell cycle by different procedures was investigated. MMuLV production was inhibited in glutamine- and isoleucine (Gln-Ile)-deprived G0/G1 cells. In contrast, butyric acid treatment, which efficiently arrested the cells at the G0/G1 phase of the cell cycle, did not inhibit MMuLV production. Furthermore, the inhibition of MMuLV production caused by either Gln-Ile deprivation or by interferon (IFN) treatment was overcome by butyric acid treatment. Thus, the replication of MMuLV could be dissociated from cell proliferation. The inhibition of MMuLV production in Gln-Ile-deprived cell cultures was compared to the inhibitory effect of IFN, which is known to affect budding and release of the virus. Rates of MMuLV protein synthesis were not affected in both the IFN-treated and Gln-Ile-deprived cells. However, processing of the viral polyprotein Pre65gag into p30 was blocked in the Gln-Ile-deprived cells. Furthermore, whereas in IFN-treated cells, MMuLV accumulated on the cell surface and could be released upon treatment with trypsin, in Gln-Ile-deprived cells, no virions were released by such treatment. These results indicate that in cells arrested by Gln-Ile deprivation, MMuLV is inhibited at a posttranslation step. This step appears to precede the anti-MMuLV block induced by IFN.
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PMID:Regulation of Moloney murine leukemia virus replication in chronically infected cells arrested at the G0/G1 phase. 258 48


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