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Biomedical subjects

A T Matheson

Publications and source records attributed to A T Matheson.

At least 37 records · Page 2Linked to original sources
PubMed1984

Purification, properties, and N-terminal amino acid sequence of certain 50S ribosomal subunit proteins from the archaebacterium Halobacterium cutirubrum.

Sixteen ribosomal proteins (r-proteins) from the 50S ribosomal subunit of the archaebacterium Halobacterium cutirubrum have been purified and their amino acid composition and partial N-terminal amino acid sequence have been determined. These proteins as a group are much more acidic than the large subunit r-proteins from eubacteria or eukaryotes. Little sequence homology is evident between the 50S subunit archaebacterial r-proteins and the equivalent proteins from the eubacterium Escherichia coli.

Amino Acid Sequence↗
PubMed1982

Chronic exposure of coho salmon to sublethal concentrations of copper.--I. Effect on growth, on accumulation and distribution of copper, and on copper tolerance.

1. Coho salmon, exposed to sublethal levels of aqueous copper (1/4 and 1/2 LC50), lost appetite and ceased growing or showed decreased rates of growth. 2. Recovery of appetite and growth rate was faster in fish exposed to 1/4 of the LC50 than in those exposed to 1/2 of the LC50. 3. Copper levels were elevated in liver gill and kidney of exposed fish with the liver tissue accumulating a much larger amount of the metal than any other tissue. 4. The concentration of liver copper became constant at about the time that growth rate recovered. 5. The exposed fish exhibited much higher resistance to elevated aqueous copper levels than did the controls. 6. The results suggest that coho salmon may become acclimated to higher levels of copper and that acclimated fish are more tolerant to copper than control animals.

Animals↗
PubMed1982

Chronic exposure of coho salmon to sublethal concentrations of copper--II. Distribution of copper between high- and low-molecular-weight proteins in liver cytosol and the possible role of metallothionein in detoxification.

1. Liver cytosol samples from juvenile coho salmon exposed over a 14-week period to 70 micrograms/l (1/4 LC50) or 140 micrograms/l (1/2 LC50), were separated into high-molecular-weight and low-molecular-weight fractions by column chromatography on Sephadex G-75, and compared to similar samples obtained from control fish. 2. The levels of copper in the low-molecular-weight function of fish exposed to 70 micrograms/l were not significantly increased over control values for the first 6 weeks but then increased rapidly, while those of fish exposed to 140 micrograms/l increased substantially in the first 2-4 weeks of exposure, then levelled off. 3. In the exposed fish the levels of copper in the high-molecular-weight fraction were not significantly elevated above control levels over the first 8-10 weeks but then increased significantly. 4. The low-molecular-weight fractions of exposed fish were shown to contain increasing levels of metallothionein. The metallothionein was isolated on DEAE-cellulose and characterized by amino acid analyses.

Animals↗
PubMed1982

Mapping evolution with ribosome structure: intralineage constancy and interlineage variation.

Ribosomal small subunits are organized in three general structural patterns that correspond to the eubacterial, archaebacterial, and eukaryotic lineages. Within each of these lineages, ribosomal structure is highly conserved. Small subunits from all three lineages share a common overall structure except for the following differences: (i) small subunits from archaebacteria and from the cytoplasmic component of eukaryotes both contain a feature on the head of the subunit, the archaebacterial bill, that is absent in eubacteria, and (ii) eukaryotic small subunits contain additional regions of density at the base of the subunit, the eukaryotic lobes, that are absent in archaebacteria and in eubacteria. We interpret the intralineage conservation of ribosomal three-dimensional structure as forming a phylogenetic basis for regarding archaebacteria, eubacteria, and eukaryotes as primitive lines. Although our data are separate and independent from those of Woese and Fox, they lend further support to their proposal [Woese, C. R. & Fox, G. E. (1977) Proc. Natl. Acad. Sci. USA 74, 5088-5090]. These data also provide a simple, rapid, and accurate method for classifying organisms and for identifying new lineages. Finally, interlineage variation of ribosomal structure is used to establish a rigorous framework for considering the evolution of these three lines.

Animals↗
PubMed1980

Sequence homologies in the N-terminal region of the ribosomal 'A' proteins from Methanobacterium Thermoautotrophicum and Halobacterium cutirubrum.

The ribosomal 'A' protein from the methanogen, Methanobacterium thermoautotrophicum, has been isolated and purified. The amino acid composition and mobility on two-dimensional gels indicates that this protein shows characteristics similar to the equivalent protein from the extreme halophile, Halobacterium cutirubrum, and is significantly different from the equivalent protein from other bacteria. The first 48 residues of the methanogenic 'A' protein were sequenced and showed a large amount of sequence homology to the H. cutirubrum 'A' protein. When the sequences of these two proteins were compared to the 'A' protein from other procaryotes (eubacteria), much less homology was evident. These results support the hypothesis (Woese, C.R. and Fox, G.F., (1977) Proc. Natl. Acad. Sci. U.S.A. 74, 5088-5090) of two procaryotic lines of evolutionary descent, the eubacteria and the archaebacteria, the latter including the methanogens and the extreme halophiles. The sequence data from the 'A' proteins also indicate that, phylogenetically, the archaebacteria are much closer to the cytoplasmic components of eucaryotes than they are to the eubacteria (or 'true bacteria').

Amino Acid Sequence↗
PubMed1979

The N-terminal sequence of the ribosomal 'A' protein from two moderate halophiles, Vibrio costicola and an unidentified moderate (NRCC 11227).

The 'A' protein, equivalent to ribosomal protein EL7/L12 from Escherichia coli, has been isolated and purified from two moderate halophiles Vibrio costicola and NRCC 11227. The 'A' protein from V. costicola contained an N-terminal serine and separated into two forms on DEAE-cellulose and two-dimensional electrophoresis while the equivalent protein in NRCC 11227 contained an N-terminal alanine residue and was present in only one form. The amino acid composition and mobility on two-dimensional gels indicated these proteins were very similar to EL7/L12. The first 38 residues of the 'A' proteins were sequenced and compared to the equivalent protein from E. coli and the extreme halophile Halobacterium cutirubrum. The N-terminal region of the 'A' protein from both moderate halophiles showed substantial homology to EL 12 (75--80%) but no evidence of any homology to the equivalent protein from the extreme halophile. The ribosomal proteins equivalent to ES1A in E. coli were also isolated and their amino acid compositions determined.

Amino Acid Sequence↗
PubMed1979

Structural homologies in alanine-rich acidic ribosomal proteins from procaryotes and eucaryotes.

The amino acid composition and amino-terminal sequence have been determined for the alanine-rich, acidic ribosomal 'A' protein (equivalent to Escherichia coli L7/L12) from three procaryotic cell types that live under extreme environmental conditions (Arthrobacter glacialis, Clostridium pasteurianum, and Bacillus stearothermophilus) as well as from wheat germ, a eucaryote source. These data are compared with previously published 'A' protein sequences from other procaryotes and eucaryotes. All the procaryotic 'A' proteins, with the exception of the very acidic 'A' protein from Halobacterium cutirubrum, show similar charge, size, and amino acid composition, as well as an extensive sequence homology in the N-terminal region. Some differences are observed between gram-negative and gram-positive bacteria. The 'A' proteins from eucaryotes contain two tyrosine molecules, an amino acid absent in procaryotic 'A' proteins, as well as a reduced number of valine residues and an increased amount of aspartic acid. The N-terminal sequence of wheat germ 'A' protein shows considerable homology with other eucaryotic 'A' proteins and also with H. cutirubrum. It also shows some sequence homology with E. coli 'A' proteins.

Alanine↗
PubMed1978

An enhanced thermostability in thermophilic 5-S ribonucleic acids under physiological salt conditions.

The secondary structure of 5-S rRNAs of Thermus aquaticus (an extreme thermophile), Bacillus stearothermophilus (a moderate thermophile) and Escherichia coli (a mesophile) was compared using thermal denaturation techniques under varying ionic conditions. At a low ionic strength (10 mM K+), the Tm of T. aquaticus 5-S RNA differed by only 1 degrees C from that of E. coli RNA and the molecule was fully denatured well below the optimum growth temperature of the thermophile. The internal Na+, K+ and Mg2+ concentrations of T. aquaticus cells were determined to be 91 mM, 130 mM and 59 mM, respectively. Under these salt conditions, T. aquaticus 5-S RNA was significantly more stable than E. coli RNA and the 5-S RNA from B. stearothermophilus was intermediate as is its optimum growth temperature. The results suggest that the thermostability of macromolecules from thermophilic organisms may be specially dependent on the internal salt concentration. Furthermore, under these salt conditions, most of the secondary structure of the RNA remained stable at the optimum growth temperatures suggesting that ribosomal RNAs of thermophilic organisms contribute more to the thermostability of the ribosome than previously thought.

Base Sequence↗
PubMed1978

The 5-S RNA . protein complex from an extreme halophile, Halobacterium cutirubrum. Purification and characterization.

A 5-S RNA . protein complex has been isolated from the 50-S ribosomal subunit of an extreme halophile, Halobacterium cutirubrum. The 50-S ribosomal subunit from the extreme halophile requires 3.4 M K+ and 100 mM Mg2+ for stability. However, if the high K+ concentration is maintained but the Mg2+ concentration lowered to 0.3 mM, the 5-S RNA . protein complex is selectively extracted from the subunit. After being purified on an Agarose 0.5-m column the complex had a molecular weight of about 80000 and contained 5-S RNA and two proteins, HL13 and HL19, with molecular weights (by sedimentation equilibrium) of 18700 and 18000, respectively. No ATPase or GTPase activity could be detected in the 5-S RNA . protein complex. The amino acid composition and electrophoretic mobility on polyacrylamide gels indicated both proteins were much more acidic than the equivalent from Escherichia coli or Bacillus stearothermophilus. Partial amino acid sequence data suggest HL13 is homologous to EL18 and HL19 to EL5.

Adenosine Triphosphatases↗
PubMed1978

Nucleotide sequence of Halobacterium cutirubrum ribosomal 5 S ribonucleic acid. An altered secondary structure in halophilic organisms.

The nucleotide sequence of ribosomal 5 S RNA from a halophilic bacterium, Halobacterium cutirubrum, grown in 4 M sodium chloride is U-U-A-A-G-G-C-G-G-C-C-A-U-A-G-C-G-G-U-G-G-G-G-U-U-A-C-U-C-C-C-G-U-A-C-C-C-A-U-C-C-C-G-A-A-C-A-C-G-G-A-A-G-A-U-A-A-G-C-C-C-G-C-C-U-G-C-G-U-U-C-C-G-G-U-C-A-G-U-A-C-U-G-G-A-G-U-G-C-G-A-G-C-C-U-C-U-G-G-G-A-A-A-U-C-C-G-G-U-U-C-G-C-C-G-C-C-U-A-C-U. This nucleotide sequence is the longest prokaryotic 5 S rRNA to be reported and unlike other 5 S species does not contain a terminal mononucleoside diphosphate residue at its 5'-end. When compared to other 5 S rRNA's, the sequence homology is greatest (about 68%) with Bacillus subtilis; there is a lower but similar degree of homology (about 58%) with either Escherichia coli or human 5 S RNA. The comparisons further indicate that among 5 S RNA's, eleven of the nucleotide residues are unique to H. cutirubrum. Estimates of the secondary structure of the H. cutirubrum 5 S RNA molecule contain one additional stable hairpin loop which is not found in other 5 S rRNA species; this unusual structure is probably an adaptation to the high salt environment within H. cutirubrum cells.

Base Sequence↗
PubMed1977

Nucleotide sequence of Thermus aquaticus ribosomal 5 S ribonucleic acid. Sequence homologies in thermophilic organisms.

The nucleotide sequence of ribosomal 5 S RNA from Thermus aquaticus grown at 75 degrees is p(A)-A-U-C-C-C-C-G-C-C-C-U-U-A-G-C-G-G-C-G-U-G-G-A-A-C-A-C-C-C-G-U-U-C-C-C-A-U-U-C-C-G-A-A-C-A-C-G-G-A-A-G-U-G-A-A-A-C-G-C-G-C-C-A-G-C-G-C-C-G-A-U-G-G-U-C-A-C-U-G-G-G-A-C-C-G-C-A-G-G-G-U-C-C-U-G-G-A-G-A-G-U-A-G-G-U-G-C-U-G-G-U-G-C-G-G-G-G-A-(U). The major molecular species is 120 nucleotides long; some molecules are one or two nucleotides shorter with one less nucleotide at either or both termini. When compared to other 5 S rRNAs, the sequence homology was greater with a thermophile bacterium (Bacillus stearothermophilus) than with mesophilic species. The comparisons further indicate that among prokaryotes, eleven of the nucleotide residues in T. aquaticus 5 S RNA may be largely restricted to thermophiles. Possible models for the secondary structure of T. aquaticus 5 S rRNA are discussed with respect to products of limited digestion and the unique nucleotides.

Base Sequence↗
PubMed1976

The properties of ribosomal proteins from a moderate halophile.

The ribosomes from the extreme halophile Halobacterium cutirubrum are unusual in that their ribosomal proteins are acidic rather than basic as is the case with almost all bacterial ribosomes (Bayley, S.T. (1966) J. Mol. Biol. 15, 420-427). To determine whether the ribosomes of a moderate halophile show similar properties the ribosomal proteins from an unidentified moderate halophile, which grows over a wide range of NaCl concentrations (0.04-4.3 M), were compared to those of Escherichia coli and H. cutirubrum. The proteins are slightly more acidic than those of E. coli but much less acidic than those from the extreme halophile as judged by their mobility on polyacrylamide gels and their amino acid composition. The electrophoretic profile on polyacrylamide gels of the ribosomal proteins from the moderate halophile is similar whether the cells are grown in 0.5 M or 4.25 M NaCl.

Amino Acids↗