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:2.7.7.48 (transcriptase)
9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We scrutinized the possible existence of human prepro-THR messenger RNA (mRNA) and of its posttranslational processing products in the human placenta. Human placental mRNA of preproTRH was found to have a single species identical to that predicted from the hypothalamic mRNA, and could be reverse transcribed to complementary DNA (cDNA) encoding preproTRH in a size similar to the hypothalamic counterpart by means of reverse-transcriptase-polymerase chain reaction. Five different intervening peptides, designated human TRH-associated peptide (hTAP) [hTAP-1, preproTRH(90-111); hTAP-2, preproTRH(120-132); hTAP-3, preproTRH(141-149); hTAP-4, preproTRH(158-183); hTAP-5, preproTRH(192-224)], and a TRH precursor comprising the TRH progenitor sequence (octa-TRH) were synthesized, and six different antisera raised against individual peptides were used to develop specific RIA systems. Significant concentrations of hTAP-5 and octa-TRH-like immunoreactivities were quantitated in acid extracts of human placentae. In human hypothalamic extracts, immunoreactivities of hTAP-3, hTAP-4, hTAP-5, and octa-TRH, were apparently detected. Chromotographic analysis showed a single peak corresponding to each authentic peptide in RIA systems of hTAPs detected. In placentae, a single peak of octa-TRH-like substance was observed, and two octa-TRH-like substances with different molecular weights detected in hypothalami. The present data indicate that unique posttranslational processing steps of human preproTRH differ in human placentae and hypothalami, and that the human tissues involve profound amounts of several preproTRH-related peptides which do not comprise the TRH progenitor sequence.
...
PMID:Different posttranslational processing of human preprothyrotropin-releasing hormone in the human placenta and hypothalamus. 146 61

One surprising outcome of applying the techniques of protein engineering to the enzyme tyrosyl-transfer RNA synthetase was that the enzyme's activity could actually be increased by a specific sequence change. In particular, altering residue threonine 51 to a proline (mutant TP51) increased the enzyme's affinity for tyrosyl adenylate complexes. The non-additive effect of combining the TP51 mutation with a second sequence alteration (histidine 48 to a glycine) suggested that the effect of the TP51 change might be mediated by a structural change involving the peptide backbone. To address the question of the mechanism by which the TP51 change increases the activity of tyrosyl-tRNA synthetase we have determined the structure of the mutant enzyme. We find the change has a purely local effect on the structure of the enzyme, and conclude that the increased activity of the TP51 mutant probably results from the replacement of the polar threonine residue by a non-polar group: in the wild-type enzyme substrate binding is disfavoured by the displacement of solvent from the vicinity of threonine 51. This unfavourable effect is absent in the TP51 mutant.
...
PMID:Structure of a mutant of tyrosyl-tRNA synthetase with enhanced catalytic properties. 310 91

The prevalence and clinical correlations of anti-threonyl-transfer RNA synthetase (anti-PL-7), as well as the relationship of anti-PL-7 to anti-histidyl-transfer RNA synthetase (anti-Jo-1) were studied in 109 sera from patients with myositis. Inhibition of threonine aminoacylation was used to screen for anti-PL-7. Sera from 3 patients, 2 with polymyositis and 1 with polymyositis-overlap syndrome, and a fourth serum from a patient with dermatomyositis, which was previously found to contain anti-PL-7, inhibited greater than 90% of activity (3.7% of 109 sera). All 4 sera reacted strongly in an enzyme-linked immunosorbent assay with enzyme that was either affinity purified with anti-PL-7 or was biochemically purified. There was no indication of cross-reactivity by aminoacylation inhibition or, for most sera, by enzyme-linked immunosorbent assay. Anti-PL-7 is an uncommon myositis-associated antibody that is independent of anti-Jo-1, but is directed at a functionally related enzyme.
...
PMID:Antibody to threonyl-transfer RNA synthetase in myositis sera. 312 89

O-methylthreonine (OMT), an isosteric analogue of isoleucine, markedly inhibited growth of Escherichia coli 15. This inhibition was overcome most effectively by addition of isoleucine, valine, or leucine to the medium and less effectively by addition of threonine. The dipeptide, valylleucine, also relieved the OMT-induced inhibition but only after a lag period, suggesting that valine and leucine, liberated by dipeptidase action, compete with OMT for entry into the cell. OMT was activated and transferred to transfer ribonucleic acid (RNA) by isoleucyl-RNA synthetase in vitro. The rate of OMT incorporation into protein of intact cells was comparable to that of isoleucine. In contrast to isoleucine, very high concentrations of OMT were required to inhibit threonine deaminase, and the inhibition was strictly competitive with threonine. In addition, OMT inhibited a threonine deaminase preparation desensitized to isoleucine inhibition.
...
PMID:O-methylthreonine inhibition of growth and of threonine deaminase in Escherichia coli. 429 94

The temperature-sensitive and attenuated phenotypes of the Sabin type 1 vaccine strain of poliovirus result from numerous point mutations which occurred in the virulent Mahoney virus parent. One of these mutations is located in a 3D polymerase (3Dpol) codon (U-6203-->C, Tyr-73-->His) and is involved in attenuation in common mice (M. Tardy-Panit, B. Blondel, A. Martin, F. Tekaia, F. Horaud, and F. Delpeyroux, J. Virol. 67:4630-4638, 1993). This mutation also appears to contribute to temperature sensitivity, in association with at least 1 other of the 10 mutations of the 3'-terminal part of the genome including the 3Dpol coding and 3' noncoding regions. To map the other mutation(s), we constructed poliovirus mutants by mutagenesis and recombination of Mahoney and Sabin 1 cDNAs. Characterization of these poliovirus mutants showed that a second mutation in a 3Dpol codon (C-7071-->U, Thr-362-->Ile) contributes to temperature sensitivity. A mutation in the 3' noncoding region of the genome (A-7441-->G), alone or linked to another mutation (U-7410-->C), also appeared to be involved in this phenotype. The temperature-sensitive effect associated with the 3'-terminal part of the Sabin 1 genome results from the cumulative and/or synergistic effects of at least three genetic determinants, i.e., the His-73 and Ile-362 codons of 3Dpol and nucleotide G-7441. Sequence analysis of strains isolated from patients with vaccine-associated paralytic poliomyelitis showed that these genetic determinants are selected against in vivo, although the Ile-362 codon appeared to be more stable than either the His-73 codon or G-7441. These genetic determinants may contribute to the safety of Sabin 1 in vaccines.
...
PMID:Mapping of mutations contributing to the temperature sensitivity of the Sabin 1 vaccine strain of poliovirus. 763 70

Previous mutations associated with lecithin:cholesterol acyltransferase (LCAT) deficiency have been identified using genomic DNA. To facilitate mutation analysis, we used cDNA from cultured fibroblasts which were shown to express LCAT mRNA. Using reverse-transcriptase PCR, LCAT cDNA was obtained from a 13-year-old boy with complete LCAT deficiency, characterized by low HDL-C (3 mg/dl), nondetectable initial cholesterol esterification rate, LCAT activity, and minimal LCAT mass (0.16 vs. 5-7.5 micrograms/ml). Sequencing of LCAT cDNA clones identified two mutations. A novel frameshift mutations caused by deletion of cytosine at the third nucleotide position of amino acid 168 (exon 5) predicts a disrupted protein catalytic site by converting Ser181-->Ala and creates a Pvu-II restriction site prior to premature truncation at amino acid 238. A C-->T transition results in a substitution of methionine for threonine at amino acid position 321 and creates an Nla-III restriction site on the maternal allele. Expression studies of mutant LCAT cDNA confirmed the virtual absence of LCAT activity in transfected COS-1 cells. The molecular defect in a young male with complete LCAT deficiency has been identified using fibroblast cDNA.
...
PMID:Lecithin: cholesterol acyltransferase deficiency: identification of two defective alleles in fibroblast cDNA. 765 65

We have isolated the murine cDNA homologue of the human protein tyrosine phosphatase PTP-PEST (MPTP-PEST) from an 18.5-day mouse embryonic kidney library. The cDNA isolated has a single open reading frame predicting a protein of 775 amino acids. When expressed in vitro as a glutathione S-transferase fusion protein, the catalytic domain (residues 1-453) shows intrinsic phosphatase activity. Reverse transcriptase PCR and Northern-blot analysis show that MPTP-PEST mRNA is expressed throughout murine development. Indirect immunofluorescence in COS-1 cells against a heterologous epitope tag attached to the N-terminus of MPTP-PEST, together with cellular fractionation and Western-blot experiments from different murine cell lines, indicate that MPTP-PEST is a free cytosolic protein of 112 kDa. Finally, sequence analysis indicates that the C-terminal portion of the protein contains four regions rich in proline, glutamate, serine and threonine, otherwise known as PEST sequences. These are characteristic of proteins that display very short intracellular half-lives. Despite the presence of these motifs, pulse-chase labelling experiments demonstrate that MPTP-PEST has a half-life of more than 4 h.
...
PMID:Murine protein tyrosine phosphatase-PEST, a stable cytosolic protein tyrosine phosphatase. 777 23

A cDNA coding for the beta 4 subunit of murine integrin (m beta 4) has been cloned and sequenced using mRNA from a murine lung carcinoma as the template. The 5' sequence contains two AUG codons, the second of which initiates synthesis of the mature protein. The cDNA sequence has an open reading frame coding for 1748 amino acids (aa), including a signal peptide, cysteine-rich region, serine- and threonine-rich region, transmembrane domain, and a cytoplasmic domain of over 1000 aa. Overall, the deduced m beta 4 aa sequence has 88% identity with the human beta 4 subunit (h beta 4) sequence deduced from the sequence of placental mRNA. Reverse transcriptase-polymerase chain reaction using primers flanking splice sites for two variant forms of h beta 4 transcripts provided evidence for alternate splicing of RNA in the murine spleen and to a lesser extent in the skin, uterus, and thymus but was found at only one of the two alternative sites. Five potential glycosylation sites present in the extracellular domain of h beta 4 are conserved in m beta 4. One tyrosine in the terminal region of the cytoplasmic domain (position 1600) is conserved between m beta 4 and h beta 4 and has the consensus sequence for tyrosine phosphorylation. Finally, a genomic restriction map of m beta 4 shows that the gene is about 40 kb in length. No restriction-fragment length polymorphisms were detected between BALB/c liver and BALB/c lung carcinoma DNA.
...
PMID:Sequence of a cDNA encoding the beta 4 subunit of murine integrin. 835 87

A newly identified temperature-sensitive mutant whose defect was mapped to the reovirus M1 gene (minor core protein mu2) was studied to better understand the functions of this virion protein. Sequence determination of the Ml gene of this mutant (tsH11.2) revealed a predicted methionine-to-threonine alteration at amino acid 399 and a change from proline to histidine at amino acid 414. The mutant made normal amounts of single-stranded RNA, both in in vitro transcriptase assays and in infected cells, and normal amounts of progeny viral protein at early times in a restrictive infection. However, tsH11.2 produced neither detectable progeny protein nor double-stranded RNA at late times in a restrictive infection. These studies indicate that mu2 plays a role in the conversion of reovirus mRNA to progeny double-stranded RNA.
...
PMID:Identification and characterization of a double-stranded RNA- reovirus temperature-sensitive mutant defective in minor core protein mu2. 867 44

Human membrane cofactor protein (MCP) is a widely distributed cell-associated complement-regulatory protein, and recent findings suggest that MCP may be involved in sperm-egg interaction. We have isolated four cDNA clones and one reverse transcriptase-PCR product homologous to human MCP from guinea pig testis. These clones defined five isoform classes generated from a single copy gene by alternative splicing. Reverse transcriptase-PCR revealed that two classes for the clones termed GMP1 and GM2 were predominant. GMP1 consisted of four short consensus repeats (SCRs), regions corresponding to the human serine/threonine/proline-rich C (STP(C)) domain and a human region of unknown significance, a hydrophobic region presumed to be a transmembrane domain, and a cytoplasmic region. Identity with human MCP in the SCR region was 56% at the amino acid level and 71% at the nucleotide level. GM2 had the same structure as GMP1, except that it lacked the fourth SCR, which is presumed to be essential for C3b binding of human MCP. Northern blotting analysis of various tissues revealed a significant level of MCP transcripts in testis. Guinea pig MCP is likely to have only one STP domain that is homologous to human STP(C) and is similar in this respect to human spermatozoa MCP. Gene analysis revealed a single base deletion and a lack of consensus sequences for splicing in the guinea pig regions corresponding to human STP(A) and STP(B), respectively. These results suggest that guinea pig MCP plays a more restricted role in reproduction than does human MCP.
...
PMID:Molecular cloning of guinea pig membrane cofactor protein: preferential expression in testis. 894


1 2 3 4 5 Next >>

---