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

---

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

The two glycoproteins, gp85 and gp35, of Rous-associated virus type 61 (RAV-61), were isolated from radiolabeled virions by gel electrophoresis and digested with trypsin. The chromatographic profile of the gp35 digest revealed no peaks in common with that of gp85; therefore, the smaller glycoprotein is not a cleavage product of gp85. The stoichiometry of radiolabeled RAV-61 proteins was studied by quantitative gel filtration and gel electrophoresis. Among the 11 polypeptides identified were 4 minor ones, including the beta(p91) and alpha(p64) chains of reverse transcriptase and two unidentified chains, p76 and p35; the latter two were unmasked by removing the virions' surface glycoproteins with a protease, bromelain. Virions contained some 15 to 30 molecules of reverse transcriptase.
...
PMID:Proteins of Rous-associated virus type 61: polypeptide stoichiometry and evidence that glycoprotein gp35 is not a cleavage product of gp85. 6 19

After polyadenylation in vitro of the influenza virus RNA segment which contains the coding information for the matrix protein, a cDNA copy can be made using the primer p(dT)8-dA and reverse transcriptase. The sequence of 166 nucleotides of the cDNA was determined by a modification [Brownlee, G. G. & Cartwright, E. M. (1977) J. Mol. Biol, 114, 93--117] of the plus/minus method [Sanger, F. & Coulson, A. R. (1975) J. Mol. Biol. 94, 441--481] and adaptation of the "dideoxy" method [Sanger, F., Nicklen, S. & Coulson, A. R. (1977) Proc. Natl. Acad. Sci. U.S.A. 74, 5463--5467] for sequencing DNA. The cDNA sequences is of the same sense as the mRNA for matrix protein and contains a potential initiating codon, d(ATG), at position 26--28. When matrix protein purified from virus particles was digested with chymotrypsin or trypsin and the amino acid compositions of separated peptides determined, one peptide containing nine amino acids found which had a composition corresponding to that predicted by the cDNA sequence following the first methionine codon, confirming that protein synthesis initiates at this position. The compositions of four other peptides matches those predicted from the nucleotide sequence. There is no processing of the N terminus of the protein before incorporation into the virus particle except for removal of the N-terminal methionine and addition of a "blocking" group on the resulting N-terminal serine residue.
...
PMID:Nucleotide sequence coding for the N-terminal region of the matrix protein influenza virus. 57 97

We found a type D retrovirus in a human lymphoblastoid cell line of B-cell lineage. Molecular cloning and nucleotide sequencing of the provirus genome revealed that this virus was closely related to squirrel monkey retrovirus (SMRV), and we designated this virus as SMRV-H. To investigate the relationship between these retroviruses, SMRV-H was purified from the virus-producing cells, and its biochemical properties were characterized. The cell-adhesive virus particles were successfully separated from the cell by a brief trypsin treatment and purified by velocity sedimentation. The purification of the virus was confirmed by electron microscopy. Major gag protein of the virus is phosphorylated, and has a molecular weight of 34 kDa. The virion-associated reverse transcriptase prefers Mg2+ to Mn2+. These properties of SMRV-H were almost the same as those of SMRV.
...
PMID:Purification and biochemical characterization of squirrel monkey retrovirus-H produced in a human lymphoblastoid cell line. 128 48

Nevirapine (BI-RG-587) is a potent and specific non-nucleoside inhibitor of human immunodeficiency virus type-1 reverse transcriptase. The compound is non-competitive with respect to template, primer, and nucleoside triphosphates indicating that BI-RG-587 does not act directly at the catalytic site. The binding site for this inhibitor was investigated by employing an azido photoaffinity analogue, BI-RJ-70, to covalently label the enzyme. The resulting photoadduct was subjected to enzymatic digestion by trypsin and endoproteinase lys-C and a single, highly labeled peptide was identified as residues 174-199. Sequencing of this peptide identified Tyr-181 and Tyr-188 as labeled residues.
...
PMID:Characterization of the binding site for nevirapine (BI-RG-587), a nonnucleoside inhibitor of human immunodeficiency virus type-1 reverse transcriptase. 171 87

Various combinations of inhibitors of HIV reverse transcriptase were tested for inhibition of HIV replication in order to reveal any potential synergism or antagonism. PFA, a pyrophosphate analogue, gave synergistic inhibition of HIV replication in combination with both of the thymidine analogues AZT and FLT. The combination of PFA and AZT-TP gave only additive or weakly synergistic inhibition in a reverse transcriptase enzyme assay. The combination of AZT and FLT also gave synergistic inhibition of HIV replication, whilst the combination of AZT-TP and FLT-TP gave only additive or weakly synergistic inhibition of reverse transcriptase. Thus, the synergy does not arise from effects on reverse transcriptase alone but must be owing to other, cellular factors, such as effects on nucleoside metabolism or metabolism of the analogues. The results are consistent with the hypothesis that AZT may have an alternative mechanism of inhibition other than inhibition of reverse transcriptase. The diminished cytotoxicity observed in addition to the synergistic inhibition makes these combinations attractive from the point of view of combination chemotherapy. The inhibition of HIV replication by peptides from various parts of the V3 region of gp120 whose sequences were homologous with the tryptase inhibitor trypstatin was tested. Inhibitory activity was displayed by two peptides containing cysteine in their sequence. Antibodies to two peptides containing the two conserved cysteine residues from opposite sides of the neutralizing loop of gp120 were previously associated with protection from vertical transmission of HIV. The V3 region thus seems to be important for the function of gp120 and the transmission of HIV.
...
PMID:Synergistic combinations and peptides in the inhibition of human immunodeficiency virus. 171 18

Deletions were constructed within a functional human immunodeficiency virus type 1 (HIV-1) proviral clone in order to assess the role of the envelope protein in virus particle formation. A graded exonuclease deletion technique was used to produce 12 clones with deletions of 175-308 nucleotides in the first conserved domain of envelope. This included 9 clones with frameshift deletions and 3 clones with in-frame deletions. Isogenic pairs of env deletion clones were produced with or without an additional deletion in the vif and vpr genes. Upon transfection, all clones produced virus particles, as determined by p24 antigen, reverse transcriptase, and sucrose gradient assays with conditioned media. Virus particles produced from clones with deletions in env or vif and vpr, or both regions, banded on sucrose gradients with a mobility similar to that of virus produced by the parental clone. The p24 gag capsid protein in the particles was resistant to trypsin, but the particles were disrupted by treatment with Triton X-100, suggesting the presence of a surrounding lipid bilayer. Furthermore, electron microscopic studies revealed both mature and immature virus particles derived from COS cells transfected with the env deletion clones. Cocultivation experiments with lymphoid cells and cells transfected with each of the env deletion clones demonstrated that the virus particles were noninfectious.
...
PMID:Formation of noninfectious HIV-1 virus particles lacking a full-length envelope protein. 182 17

Bacterially expressed recombinant HIV-1 reverse transcriptase is active as both a homodimer of Mr 66,000 subunits and a heterodimer of Mr 66,000 and 51,000 subunits. The heterodimer is formed by cleavage of a C-terminal fragment from one Mr 66,000 polypeptide, which occurs during purification and crystallization of reverse transcriptase. Thus, crystals obtained from purified Mr 66,000 polypeptide preparations consisted of an apparently equimolar mixture of Mr 66,000 and 51,000 polypeptides, which were apparently analogous to the Mr 66,000 and 51,000 polypeptides detected in HIV-infected cells and in virions. Limited proteolysis of the homodimer with alpha-chymotrypsin also resulted in cleavage to a stable Mr 66,000/51,000 mixture, and proteolysis with trypsin resulted in the transient formation of some Mr 51,000 polypeptide. These results are consistent with the reverse transcriptase molecule having a protease-sensitive linker region following a structured domain of Mr 51,000. Further digestion with trypsin resulted in cleavage of the Mr 51,000 polypeptide after residue 223, yielding peptides of apparent Mr 29,000 and 30,000. A minor peptide of Mr 40,000 was also produced by cleavage of the Mr 66,000 polypeptide after residue 223. About half the original Mr 66,000 polypeptides remained resistant to proteolysis and existed in complex with the above peptides in solution. During both chymotrypsin and trypsin digestion there was an increase in the reverse transcriptase activity caused by a doubling of Vmax with little change in Km for dTTP.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:HIV-1 reverse transcriptase: crystallization and analysis of domain structure by limited proteolysis. 246 81

Human immunodeficiency virus (HIV) reverse transcriptase has been purified from yeast transformed by an autoreplicating plasmid containing the retroviral DNA polymerase gene. The previously described purification procedure for the yeast-expressed reverse transcriptase [Barr, P.J., Power, M.D., Chun Ting Lee-Ng, Gibson, H. & Luciw, P. (1987) Bio/Technology 5, 486-489] has been substantially modified, leading to an increased yield and a higher degree of purity. Several biochemical properties of the enzyme are described (template specificity, effect of DNA synthesis inhibitors); interestingly, HIV reverse transcriptase is highly resistant to N-ethylmaleimide. A complex between the human retroviral enzyme and the bovine tRNALys was shown, using a direct approach, by glycerol gradient centrifugation, as well as by the protective and specific effect of the tRNALys against enzyme inactivation by thermal denaturation and trypsin digestion. A competitive type of inhibition of HIV reverse transcriptase by tRNALys, but not by tRNAVal, is observed when viral RNA or activated DNA are used as templates.
...
PMID:Human immunodeficiency virus reverse transcriptase expressed in transformed yeast cells. Biochemical properties and interactions with bovine tRNALys. 247 48

Human retroviruses have recently been linked with T cell lymphoproliferative disorders and with the acquired immune deficiency syndrome. We investigated the mechanisms for acquired pure red cell aplasia and cutaneous anergy in a patient with the chronic T gamma-lymphoproliferative disease (T gamma-LPD) syndrome. Patient marrow erythroid progenitors (BFU-E) were 17 +/- 9% of control and were selectively increased to 88-102% of control after marrow T cell depletion. Patient Leu 2+ suppressor T cells spontaneously produced high titers of human gamma-interferon and resulted in a concentration-dependent selective inhibition (74-91%) of BFU-E when co-cultured with autologous or allogeneic marrow. Conditioned media (CM) derived from patient Leu 2+ T cells similarly inhibited growth of autologous or allogeneic marrow BFU-E. The inhibitory factor derived from patient CM was acid-labile (pH 2) and sensitive to trypsin; prior treatment of patient T cells with anti-HLA-DR monoclonal antibody plus complement abrogated the suppressive effect of T cell-derived CM. Patient peripheral blood mononuclear cells (PBMC) were unable to support growth of cultured interleukin 2 (IL 2)-dependent T cells, but responded to exogenous IL 2 in vitro with a 16-21-fold augmentation, relative to control, in mitogen-induced proliferation. Antibodies to HTLV-I core proteins p19 and p24 but not to HTLV-III proteins were detected in patient serum by Western blotting; patient cultured PBMC stained (7-11%) with antibodies to p19 and p24. Patient cultured PBMC demonstrated integrated HTLV-I genomic sequences by the Southern technique and expressed both specific HTLV-I genomic sequences by RNA dot blot plus reverse transcriptase activity. Utilizing a cloned DNA probe for the beta chain of the T cell receptor gene, patient PMBC demonstrated gene rearrangements providing presumptive evidence for clonality. The presence in serum of HTLV-I p19 and p24 antibodies, the expression of p19 and p24 core antigens on patient mononuclear cells, the evidence of HTLV-I proviral integration sequences and the expression of HTLV-I genomic sequences in patient cells, indicates infection with HTLV-I and raises the possibility of an etiologic link between human retrovirus infection and some instances of large granular lymphocytic leukemia (T gamma-LPD).
...
PMID:Human T cell leukemia virus-I-associated T-suppressor cell inhibition of erythropoiesis in a patient with pure red cell aplasia and chronic T gamma-lymphoproliferative disease. 289 60

A proteolytic activity is associated with structural protein p15 in avian RNA tumor viruses. Its effect on the known intracellular viral polyprotein precursors obtained by immunoprecipitation was investigated. Cleavage of Pr76gag resulted in the sequential appearance of p15, p27, and p19. The intracellular precursor Pr180gag-pol was also cleaved by p15, whereas the intracellular glycoprotein precursors of avian RNA tumor viruses, Pr92env, remained unaffected by p15 under all conditions tested. The specificities of the antibodies used to precipitate the precursors influenced the pattern of intermediates and cleavage products obtained by p15 treatment. If virus harvested from the the Prague strain of Rous sarcoma virus, subgroup C-transformed cells at 15-min intervals was incubated at 37 degrees C for further maturation, RNA-dependent DNA polymerase activity showed an optimum of DNA synthesis with 70S viral RNA or synthetic template-primers after short incubation periods. The presence of additional p15 during incubation resulted in a shift of the enzyme activity peak toward earlier time points. Virus harvested at 3-h intervals contained significant amounts of Pr180gag-pol and Pr76gag. The addition of p15 resulted in the cleavage of Pr180gag-pol and Pr76gag, but only a few distinct low-molecular-weight polypeptides appeared. Treatment of purified RNA-dependent DNA polymerase with p15 in vitro resulted in a disappearance of the beta subunit and an enrichment of the alpha subunit. In addition, a polypeptide of 32 x 10(3) molecular weight was generated. The cleavage pattern observed differed from the one obtained by trypsin treatment.
...
PMID:Effect of p15-associated protease from an avian RNA tumor virus on avian virus-specific polyprotein precursors. 615 35


1 2 3 4 5 6 7 8 9 10 Next >>

---