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S Altman

Publications and source records attributed to S Altman.

At least 145 records · Page 8Linked to original sources
PubMed1984

Cleavage of tRNA precursors by the RNA subunit of E. coli ribonuclease P (M1 RNA) is influenced by 3'-proximal CCA in the substrates.

tRNA precursor molecules that contain the CCA sequence found at the 3' termini of all mature tRNAs are cleaved in vitro more readily by M1 RNA, the catalytic subunit of E. coli RNAase P, than precursors that lack this sequence. The sensitivity to the CCA sequence is not apparent when precursors are cleaved by the reconstituted RNAase P holoenzyme that contains both M1 RNA and the protein subunit. These results have been obtained with monomeric precursor molecules encoded by the E. coli and human chromosomes and with three dimeric precursor molecules encoded by the bacteriophage T4 genome. The data are in agreement with previous results concerning T4 tRNA biosynthesis in vivo and show that the CCA sequence is important for the processing of precursors to tRNAs.

Base Sequence↗
PubMed1984

Increased serum glycosidase activity in human hypertension.

Compared to values obtained in healthy normotensive control subjects, the serum activity of the lysosomal enzymes N-acetyl-beta-D-glucosaminidase (NAG) and beta-glucuronidase, was found to be elevated in patients with mild or borderline hypertension. The serum activity of the cytosolic enzyme lactate dehydrogenase was the same in the two groups. Serum NAG activity in hypertension was inversely correlated with glomerular filtration rate and renal plasma flow. Because of the greater variability of beta-glucuronidase activity, there were no such correlations between the serum levels of this enzyme and the measurements of renal function.

Acetylglucosaminidase↗
PubMed1983

A G43 to U43 mutation in E. coli tRNAtyrsu3+ which affects processing by RNase P.

A novel mutation in the anticodon stem of E. coli tRNA1Tyrsu3+ (G43 to U43) has been characterized. The gene coding for the mutant tRNA, carried by phage phi 80DHA61.3 a derivative of phi 80psu3+su0, produces only 20% of mature suppressor tRNA as compared with phi 80psu3+. Both the mutant tRNA precursor and mature tRNA have an altered conformation. The precursor tRNA coded for by phi 80DHA61.3 is processed by RNase P more slowly than the su3+ precursor and does not form as stable an enzyme-substrate complex as does su3+ precursor. phi 80 DHA61.3 also contains a large deletion which begins in the spacer region between the su3+ gene and the su0- gene, extends through the su0- gene and includes most of the repeated region following the tRNA genes.

Anticodon↗
PubMed1983

The RNA moiety of ribonuclease P is the catalytic subunit of the enzyme.

The RNA moieties of ribonuclease P purified from both E. coli (M1 RNA) and B. subtilis (P-RNA) can cleave tRNA precursor molecules in buffers containing either 60 mM Mg2+ or 10 mM Mg2+ plus 1 mM spermidine. The RNA acts as a true catalyst under these conditions whereas the protein moieties of the enzymes alone show no catalytic activity. However, in buffers containing 5-10 mM Mg2+ (in the absence of spermidine) both kinds of subunits are required for enzymatic activity, as shown previously. In the presence of low concentrations of Mg2+, in vitro, the RNA and protein subunits from one species can complement subunits from the other species in reconstitution experiments. When the precursor to E. coli 4.5S RNA is used as a substrate, only the enzyme complexes formed with M1 RNA from E. coli and the protein moieties from either bacterial species are active.

Bacillus subtilis↗
PubMed1983

Repeated sequences and open reading frames in the 3' flanking region of the gene for the RNA subunit of Escherichia coli ribonuclease P.

We have determined the identity of about 700 nucleotides in the 3' flanking region of the gene for M1 RNA, the RNA component of RNase P (EC 3.1.26.5). This region begins with a 113-base-pair segment of DNA, which is repeated approximately 3.5 times. The first repeating unit originates within the gene sequence for the 3' end of mature M1 RNA. The repeating units are highly conserved but diverge considerably after the partial fourth repeat. Segments of sequence homologous to the repeats have been identified both upstream in the M1 RNA transcription unit and downstream from the repeating units. Several overlapping open reading frames, with the potential to encode small basic proteins, have been identified in the repeated sequences. The structure of the M1 RNA gene 3' flanking region is very similar to the corresponding region at the Tyr T locus. In vitro and in vivo, transcription of the M1 RNA gene appears to terminate about 40 nucleotides downstream from the 3' terminus of mature M1 RNA. Therefore, an RNA processing event is involved in the biosynthesis of M1 RNA.

Base Sequence↗
PubMed1982

Unusual suppression properties of lysogens containing derivatives of phi 80 psu3+.

Nonsense codon suppressing lysogens of E. coli have been made using phi 80 psu3+-A2 and phi 80 psuoc+-A2, heat-sensitive amber and ochre suppressing derivatives, respectively, of bacteriophage phi 80. The various lysogens selected differ in strength of suppression as well as in heat sensitivity of suppressor function. Heat-resistant derivatives, some still carrying the A2 mutation, can be selected from the heat sensitive parents. Mapping experiments indicate that the phi 80 derivatives integrate at the tyrTV locus, which contains two copies of tRNA1Tyr. The origin of the various suppressor phenotypes appears to be related to the great variety of distinctive recombination events possible either between the incoming tRNA1Tyr gene and the host copies, or among the three copies of this gene in the lysogens.

Bacteriophages↗
PubMed1982

Nucleotide sequence of the gene encoding the RNA subunit (M1 RNA) of ribonuclease P from Escherichia coli.

The gene encoding the RNA subunit (M1 RNA) of RNAase P (EC 3.1.26.5) from Escherichia coli has been isolated, and its complete nucleotide sequence, including flanking regions, has been determined. The promoter region, similar to others near genes under stringent control, and the site of transcription termination have been identified. The transcript from the gene (M1 RNA) can be drawn in a secondary structure that has approximately 60% G-C base pairs. One hairpin loop of this hypothetical structure has five contiguous nucleotides complementary to invariant nucleotides in the TpsiCG loop of all E. coli tRNAs. The M1 gene, when subcloned in the plasmid pBR325, can be amplified. It directs production of functional M1 RNA. In an E. coli strain thermosensitive for RNAase P function, the size of the gene transcript is the same as in wild-type E. coli, but less mature M1 RNA is made in the mutant cells.

Base Sequence↗
PubMed1982

Increased serum N-acetyl-beta-D-glucosaminidase activity in human hypertension.

Compared to values obtained in healthy normotensive control subjects, serum activity of the lysosomal enzyme N-acetyl-beta-D-glucosaminidase (NAG) was found to be elevated in patients with untreated or treated essential hypertension and in patients with renovascular hypertension. Increased NAG activity in hypertension could not be ascribed to tissue necrosis because the serum levels of several commonly measured cytosolic enzymes were within normal limits. The kidney is a likely but unproven source of the enzyme elevation in hypertension.

Acetylglucosaminidase↗
PubMed1982

Case-mix differences between hospital outpatient departments and private practice.

The belief that patients seen in hospital outpatient departments are sicker than those patients seen by private practice physicians is examined in this article. A large scale data set developed by Robert Mendenhall at the University of Southern California and modeled on the National Ambulatory Medical Care Survey (NAMCS) is used for secondary analysis. Differences in case-mix complexity were found to be slight, using two separate techniques.

Ambulatory Care↗
PubMed1981

Properties of purified ribonuclease P from Escherichia coli.

The purified protein moiety of ribonuclease P (EC 3.1.26.5) from Escherichia coli, a single polypeptide of molecular weight approximately 17 500, has not catalytic activity by itself on several RNA substrates. However, when it is marked in vitro with an RNA species called M1 RNA, RNase P activity is reconstituted. The rate at which the purified RNase P cleaves any particular tRNA precursor molecule depends on the identity of that tRNA precursor.

Endonucleases↗
PubMed1981

An E. coli gene coding for a protamine-like protein.

Several open reading frames exist in the region of the tRNATyr/1 gene of the E. coli genome. One such sequence encodes a polypeptide 33 amino acids in length that, on the basis of size and amino acid sequence, bears a striking resemblance to the protamines found in trout sperm. DNA from the transducing phage phi 80 tRNATyr/1 su3+ directs in vitro synthesis of two small basic proteins that are not made when homologous DNA containing a deletion that overlaps both the su3+ gene and the gene for the putative protamine-like protein is used. DNA from phage that have regained the parental su3+ phenotype again direct in vitro synthesis of the basic proteins. Synthesis of basic protein is inhibited by the presence of ppGpp, as would be expected if the mRNA is part of a large RNA transcript that starts at the promoter for the tRNATyr/1 gene.

Escherichia coli↗