UMLS:C0162871 - FACTA Search

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Query: UMLS:C0162871 (abdominal aortic aneurysm)
8,664 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previous genetic analyses indicated that translational frameshifting in the--1 direction occurs within the run of six adenines in the sequence 5'-TTAAAAAACTC-3' at nucleotide positions 305-315 in IS 1, where the two out-of-phase reading frames insA and B'-insB overlap, to produce transposase with a polypeptide segment Leu-Lys-Lys-Leu at residues 84-87. IS 1 mutants with a 1 bp insertion, which encode mutant transposases with an amino acid substitution within the polypeptide segment at residues 84-87, did not efficiently mediate cointegration, except for an IS 1 mutant which encodes a mutant transposase with a Leu-Arg-Lys-Leu segment instead of Leu-Lys-Lys-Leu. An IS 1 mutant with the DNA segment 5'-CTTAAAAACTC-3' at positions 305-315 carrying the termination codon TAA in the B'-insB reading frame could still mediate cointegration, indicating that codon AAA for Lys corresponding to second, third and fourth positions in the run of adenines is the site of frameshifting. The beta-galactosidase activity specified by several IS 1-lacZ fusion plasmids, in which B'-insB is in-frame with lacZ, showed that the region 292-377 is sufficient for frameshifting. The protein produced by frameshifting from the IS 1-lacZ plasmid in fact contained the polypeptide segment Leu-Lys-Lys-Leu encoded by the DNA segment 5'-TTAAAAAACTC-3', indicating that--1 frameshifting does occur within the run of adenines.
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PMID:Identification of the site of translational frameshifting required for production of the transposase encoded by insertion sequence IS 1. 133 29

The fate of the amino termini of nascent polyalanine, polyserine, and polylysine was monitored by fluorescence techniques as each was translated on Escherichia coli ribosomes. A coumarin probe was placed at the alpha-amino group of a synthetic elongator alanyl-tRNA or a synthetic initiator alanyl-tRNA or at the epsilon-amino group of natural lysyl-tRNA, and each was used to nonenzymatically initiate peptide synthesis. The fluorescent alanyl-tRNAs containing an AAA anticodon were used to initiate polyserine (with a synthetic tRNA(Ser] or polyalanine synthesis from a poly(uridylic acid) template. The fluorescent lysyl-tRNA was used to initiate polylysine synthesis from poly(adenylic acid). Changes in the fluorescence of the amino-terminal coumarin were examined to characterize the environment of the probe as the nascent peptides were extended. Protection from proteolysis and the binding of anti-coumarin antibodies or Fab fragments suggest that the amino terminus of each polypeptide is protected from interaction with proteins (Mr greater than 28,000) until the peptides are extended to an average length of 40-50 residues; however, the fluorescence from the amino terminus of shorter nascent polyalanine and polyserine peptides was readily quenched by methyl viologen (Mr = 257), indicating ribosomes do not shield the nascent peptide from molecules of this size. The data appear to indicate that polyalanine, polyserine, and polylysine are extended from the peptidyl transferase into a protected region of the ribosome such as a groove or tunnel but that this region is readily accessible to small molecules.
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PMID:Fluorescence characterization of the environment encountered by nascent polyalanine and polyserine as they exit Escherichia coli ribosomes during translation. 154 May 93

Acid sphingomyelinase (ASM; HGMW-approved symbol, SMPD1) is the lysosomal phosphodiesterase that hydrolyzes sphingomyelin to ceramide and phosphocholine. The deficient activity of this enzyme results in Types A and B Niemann-Pick disease (NPD). The full-length cDNA encoding human ASM has been isolated and characterized (E. H. Schuchman, M. Suchi, T. Takahashi, K. Sandhoff, and R. J. Desnick (1991) J. Biol. Chem. 66:8531-8539), and the ASM gene has been localized to chromosomal region 11p15.1-p15.4 (L. V. Pereira, R. J. Desnick, D. Adler, C. M. Disteche, and E. H. Schuchman (1991) Genomics 9:229-234). Using the cDNA as a probe, a genomic clone containing the ASM genomic region was isolated and the complete nucleotide sequence of the human ASM gene, including 1116 and 468 nucleotides upstream and downstream from the ASM coding region, respectively, was determined. This housekeeping gene contained six exons ranging in size from 77 to 773 bp and five introns ranging in size from 153 to 1059 bp. Exon 2 was unusually large and encoded 258 amino acids, or about 44% of the mature ASM polypeptide. The alternatively spliced 172-bp type 1-specific sequence was encoded by exon 3, whereas the type 2-specific sequence was located at the 5' end of intron 2. An analysis of the intron/exon junctions revealed that there was a weak donor splice site (AAA gtgagg) at the exon 3/intron 3 junction which occasionally leads to alternative splicing of exon 3 and the occurrence of the type 2 and 3 ASM transcripts. A single Alu1 element in the reverse orientation was in intron 2, immediately downstream from the type 2-specific sequence.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Structural organization and complete nucleotide sequence of the gene encoding human acid sphingomyelinase (SMPD1). 174 Mar 30

The genes for alkaline protease (apr[BamP]) and neutral protease (npr[BamP]) from Bacillus amyloliquefaciens have been isolated and expressed in Bacillus subtilis. The DNA sequences of apr[BamP] and npr[BamP] revealed, in each case, the presence of a large open reading frame. The inferred amino acid sequence of either gene contained a signal sequence and an additional polypeptide sequence ('pro' sequence) preceding the mature protein. Based on DNA sequence, the start point of translation has been identified as amino acid residue - 107 for apr[BamP] and -221 for npr[BamP]. To demonstrate that the start point of translation of apr[BamP] in vivo is probably at codon -107, codon -103 (AAA) was changed to an ochre (TAA) by site-directed mutagenesis. Alkaline protease was produced from this ochre mutant derivative of apr[BamP] only when the host strain was Su+. The presence of a pro sequence may be common to all of the secreted proteases from bacilli.
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PMID:Genes for alkaline protease and neutral protease from Bacillus amyloliquefaciens contain a large open reading frame between the regions coding for signal sequence and mature protein. 609 Mar 91

Previous results from this laboratory indicated that, in Escherichia coli K12, a new class of missense suppressors, which read the lysine codons AAA and AAG, may be misacylated lysine transfer RNAs. We therefore isolated and determined the nucleotide sequence of the lysine tRNA from two of the suppressor strains. In each case, we found both wild-type and mutant species of lysine tRNA, a result consistent with evidence that there are two genes for lysine tRNA in the E coli genome. The wild-type sequence was essentially identical to that reported for lysine tRNA from E. coli B. The mutant species isolated from each suppressor strain had a U for C70 nucleotide substitution, demonstrating that the AAG suppressor is a mutant lysine tRNA. The nucleotide substitution in the amino acid acceptor stem is consistent with the in vivo evidence that the suppressor corrects AAA and AAG missense mutations by inserting an amino acid other than lysine during polypeptide synthesis. This report represents the first verification of missense suppression caused by misacylation of a mutant tRNA.
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PMID:Nucleotide substitution in the amino acid acceptor stem of lysine transfer RNA causes missense suppression. 636 14

After our first observation of codon context effects in missense suppression ( Murgola & Pagel , 1983), we measured the suppression of missense mutations at two positions in trpA in Escherichia coli. The suppressible codons in the trpA messenger RNA were the lysine codons, AAA and AAG, and the glutamic acid codons, GAA and GAG. The mRNA sites of the codons correspond to amino acids 211 and 234 of the trpA polypeptide, positions at which glycine is the wild-type amino acid. Our data demonstrated codon context effects with both pairs of codons. The results indicate that suppression of AAA and AAG by mutant lysine transfer RNAs was more efficient at 211 than at 234, whereas suppression of GAA and GAG by two different mutant glycine tRNAs was more efficient at 234 than at 211. In general, the context effects were more pronounced with GAG and AAG than with GAA and AAA. (In some instances it appeared that suppression of GAA or AAA at a given position was more effective than suppression of GAG or AAG.) By contrast, no context effects were observed with a glyT suppressor of AAA and AAG, a glyT GAA/G-suppressor, and a glyU suppressor of GAG. Our observation of this phenomenon in missense suppression demonstrates that codon context can affect polypeptide elongation and that the effects can be different depending on the codons and tRNAs examined. It is suggested that tRNA-tRNA interaction on the ribosome is involved in the observed context effects.
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PMID:Codon context effects in missense suppression. 637 55

The Xy1R protein positively controls expression from the Pseudomonas putida TOL plasmid sigma 54-dependent Pu and Ps promoters, in response to the presence of aromatic effectors such as m-xylene, m-methylbenzyl alcohol, and p-chlorobenzaldehyde in the culture medium. Xy1R also autoregulates its own synthesis. A mutant Xy1R regulator called Xy1R7 was isolated after nitrosoguanidine mutagenesis of the wild-type gene and phenotypic selection for mutants that had acquired the ability to recognize m-nitrotoluene, a nitroarene that is not an effector for the wild-type regulator. The mutant regulator exhibited a single point mutation that resulted in a change in codon 172 (GAA-->AAA), which should result in a Glu-->Lys change in the polypeptide chain. The effector profile of the mutant regulator was determined by measuring beta-galactosidase from a fusion of the Pu promoter to a promoterless lacZ gene. The results showed that the mutant regulator had acquired the ability to recognize m-nitrotoluene, and retained the wild-type regulator's ability to recognize most of the wild-type effectors. Full transcriptional activation of the Pu promoter by Xy1R7, as with the wild-type Xy1R protein, requires its full modular structure, namely the sigma 54 recognition site, the integration host factor binding site, and the upstream activation sequences. The Xy1R7 regulator did not stimulate transcription from the Ps promoter in response to the presence of its effectors, and autoregulated its own synthesis at low levels.
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PMID:Genetic evidence for activation of the positive transcriptional regulator Xy1R, a member of the NtrC family of regulators, by effector binding. 813 29

Highly purified Golgi membranes were isolated from the scaly green flagellate Scherffelia dubia using osmotic shock for controlled cell rupture, differential centrifugations and a discontinuous sucrose density gradient centrifugation. Three Golgi membrane fractions (based on the distribution of IDPase activity in the gradient) at densities 1.14 g/ml, 1.17 g/ml and 1.20 g/ml were obtained. The specific IDPase activity in these fractions was enriched about 78-fold compared to the crude cell homogenate. The Golgi membrane fractions were further characterized by electron microscopy, SDS-PAGE and lectin blotting. The low density fraction (1.14 g/ml) contained two distinct vesicle populations and scale precursors associated with the outer surface of the larger-size vesicles. The medium density fraction (1.17 g/ml) contained in addition to the larger vesicles, multilamellate vesicles and semicircular cisternae. Finally, in the high density fraction (1.20 g/ml) in addition to small and large vesicles, a tubular membrane reticulum was observed. The three Golgi membrane fractions revealed the same complex overall polypeptide composition when analyzed by SDS-PAGE, but gradual quantitative differences in the polypeptide profile between fractions were observed. The lectins GNA, DSA, and AAA bound to several glycoproteins in all Golgi membrane fractions. Deglycosylation with N-glycosidase F showed that all carbohydrate structures recognized by GNA and DSA, and one recognized by AAA were of the N-glycosidic type indicating the presence of both "high mannose" and "processed" N-glycans in the Golgi apparatus of S. dubia.
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PMID:Isolation and characterization of the Golgi apparatus of a flagellate scaly green alga. 822 93

A comparative study of the chymotrypsin-like activity of the purified recombinant ClpP protease and the multicatalytic proteinase from rat liver is presented. The peptidase activity of both enzymes has been analyzed with several synthetic fluorogenic peptides, containing either aromatic or nonpolar amino acids in their P1 position. The respective Vmax, Km, and Vmax/Km were calculated from kinetic experiments. The substrate specificity of the multicatalytic proteinase, as expressed by Vmax/Km values, indicate the following substrate preference: N-Suc-IIW-MCA > N-Suc-LY-MCA > N-Suc-LLVY-MCA > or = N-Suc-AAF-MCA > N-Cbz-GGL-beta-NA > Glut-GGF-beta-NA > FPAM-4-MNA. In the case of the ClpP the order of preference is: N-Suc-LY-MCA > N-Suc-IIW-MCA > N-Suc-LLVY-MCA > or = N-Suc-AAF-MCA > or = N-Cbz-GGL-beta-NA > FPAM-4-MNA (where: N-Suc, N-succinyl-; MCA, 7-amido-4-methyl coumarin; beta-NA, beta-naphthylamide; N-Cbz, N-benzyloxycarbonyl-; 4-MNA, 4-methoxy-beta-naphthylamide; Glut, glutaryl. This similar substrate specificity is further supported by the lack of activity of both enzymes against SY-MCA and N-Suc-AAPF-MCA (known substrates of chymotrypsin), by very reduced activity against N-Suc-AAA-MCA and by no significant activity against LG-beta-NA. The results of mixed substrate experiments have shown that all the peptides that are substrates seem to be hydrolyzed by a single class of chymotrypsin-like site in both enzymes. The substrate specificity studies suggest a possible evolutionary relationship between the catalytic component of the ClpP of Escherichia coli and the multicatalytic proteinase chymotrypsin-like catalytic component. This conclusion is further supported by other circumstantial evidence: the fact that affinity-purified anti-ClpP antibodies cross-react with two polypeptide components of the rat liver multicatalytic proteinase complex, presented here and also shown previously; the known resemblance of both structures at the electron microscope level; and their reported role in the degradation of NH2-end rule substrates.
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PMID:A comparative study of the chymotrypsin-like activity of the rat liver multicatalytic proteinase and the ClpP from Escherichia coli. 840 53

The mechanism of selective protein degradation of membrane proteins in mitochondria has been studied employing a model protein that is subject to rapid proteolysis within the inner membrane. Protein degradation was mediated by two different proteases: (i) the m-AAA protease, a protease complex consisting of multiple copies of the ATP-dependent metallopeptidases Yta1Op (Afg3p) and Yta12p (Rcalp); and (ii) by Ymelp (Ytallp) that also is embedded in the inner membrane. Ymelp, highly homologous to Yta1Op and Yta12p, forms a complex of approximately 850 kDa in the inner membrane and exerts ATP-dependent metallopeptidase activity. While the m-AAA protease exposes catalytic sites to the mitochondrial matrix, Ymelp is active in the intermembrane space. The Ymelp complex was therefore termed 'i-AAA protease'. Analysis of the proteolytic fragments indicated cleavage of the model polypeptide at the inner and outer membrane surface and within the membrane-spanning domain. Thus, two AAA proteases with their catalytic sites on opposite membrane surfaces constitute a novel proteolytic system for the degradation of membrane proteins in mitochondria.
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PMID:AAA proteases with catalytic sites on opposite membrane surfaces comprise a proteolytic system for the ATP-dependent degradation of inner membrane proteins in mitochondria. 886 50

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