Role of directional mutation pressure in the evolution of the eubacterial genetic code.
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Anticodon↗
Biomedical subjects
T Ohama
Publications and source records attributed to T Ohama.
Organization and codon usage of the streptomycin operon in Micrococcus luteus, a bacterium with a high genomic G + C content.
The DNA sequence of the Micrococcus luteus str operon, which includes genes for ribosomal proteins S12 (str or rpsL) and S7 (rpsG) and elongation factors (EF) G (fus) and Tu (tuf), has been determined and compared with the corresponding sequence of Escherichia coli to estimate the effect of high genomic G + C content (74%) of M. luteus on the codon usage pattern. The gene organization in this operon and the deduced amino acid sequence of each corresponding protein are well conserved between the two species. The mean G + C content of the M. luteus str operon is 67%, which is much higher than that of E. coli (51%). The codon usage pattern of M. luteus is very different from that of E. coli and extremely biased to the use of G and C in silent positions. About 95% (1,309 of 1,382) of codons have G or C at the third position. Codon GUG is used for initiation of S12, EF-G, and EF-Tu, and AUG is used only in S7, whereas GUG initiates only one of the EF-Tu's in E. coli. UGA is the predominant termination codon in M. luteus, in contrast to UAA in E. coli.
Amino Acid Sequence↗
[Clinical study of the measurement of tissue polypeptide antigen in patients with breast cancer].
Tissue polypeptide antigen (TPA) concentrations in patients with breast cancer were measured using a radioimmunoassay (RIA) kit. Although this RIA kit presented some problems in the dilution test of high-concentration samples, it was found to be adequate for clinical use. It was shown that the measurement of serum TPA concentration was useful in monitoring the local recurrence, for the early diagnosis of distant metastasis and for evaluating the therapeutical effect after surgery. TPA concentration showed no correlation with CEA concentration. Therefore, in order to raise the rate of diagnostic success, simultaneous measurement of both TPA and CEA was essential.
Adult↗
Evolution of multicellular animals as deduced from 5S rRNA sequences: a possible early emergence of the Mesozoa.
The nucleotide sequences of 5S rRNA from a mesozoan Dicyema misakiense and three metazoan species, i.e., an acorn-worm Saccoglossus kowalevskii, a moss-animal Bugula neritina, and an octopus Octopus vulgaris have been determined. A phylogenic tree of multicellular animals has been constructed from 73 5S rRNA sequences available at present including those from the above four sequences. The tree suggests that the mesozoan is the most ancient multicellular animal identified so far, its emergence time being almost the same as that of flagellated or ciliated protozoans. The branching points of planarians and nematodes are a little later than that of the mesozoan but are clearly earlier than other metazoan groups including sponges and jellyfishes. Many metazoan groups seem to have diverged within a relatively short period.
Animals↗
The nucleotide sequences of 5S rRNAs from a sea-cucumber, a starfish and a sea-urchin.
The nucleotide sequences of 5S rRNA from three echinoderms, a sea-cucumber Stichopus oshimae, a starfish Asterina pectinifera and a sea-urchin Hemicentrotus pulcherrimus have been determined. These 5S rRNAs are all 120 nucleotides long. The echinoderm sequences are more related to the sequences of proterostomes animals such as mollusc, annelids and some others (87% identity on average) than to those of vertebrates (82% identity on average).
Animals↗
Fresh-water planarias and a marine planaria are relatively dissimilar in the 5S rRNA sequences.
The nucleotide sequences from fresh-water Dugesia japonica and marine Planocera reticulata have been determined. The similarity between these two species is only 69%. The Planocera sequence reveals nearly 80% similarity (72-81%) to the sequences of multicellular animals, while the Dugesia sequences are considerably different from them (66-73%).
Animals↗
Nucleotide sequences of 5S rRNAs from four jellyfishes.
The nucleotide sequences of 5S rRNAs from four jellyfishes, Spirocodon saltatrix, Nemopsis dofleini, Aurelia aurita and Chrysaora quinquecirrha have been determined. The sequences are highly similar to each other. A fairly high similarity was also found between these jellyfishes and a sea anemone, Anthopleura japonica.
Animals↗
Regular spliceosomal introns are invasive in Chlamydomonas reinhardtii: 15 introns in the recently relocated mitochondrial cox2 and cox3 genes.
In the unicellular green alga, Chlamydomonas reinhardtii, cytochrome oxidase subunit 2 (cox2) and 3 (cox3) genes are missing from the mitochondrial genome. We isolated and sequenced a BAC clone that carries the whole cox3 gene and its corresponding cDNA. Almost the entire cox2 gene and its cDNA were also determined. Comparison of the genomic and the corresponding cDNA sequences revealed that the cox3 gene contains as many as nine spliceosomal introns and that cox2 bears six introns. Putative mitochondria targeting signals were predicted at each N terminal of the cox genes. These spliceosomal introns were typical GT-AG-type introns, which are very common not only in Chlamydomonas nuclear genes but also in diverse eukaryotic taxa. We found no particular distinguishing features in the cox introns. Comparative analysis of these genes with the various mitochondrial genes showed that 8 of the 15 introns were interrupting the conserved mature protein coding segments, while the other 7 introns were located in the N-terminal target peptide regions. Phylogenetic analysis of the evolutionary position of C. reinhardtii in Chlorophyta was carried out and the existence of the cox2 and cox3 genes in the mitochondrial genome was superimposed in the tree. This analysis clearly shows that these cox genes were relocated during the evolution of Chlorophyceae. It is apparent that long before the estimated period of relocation of these mitochondrial genes, the cytosol had lost the splicing ability for group II introns. Therefore, at least eight introns located in the mature protein coding region cannot be the direct descendant of group II introns. Here, we conclude that the presence of these introns is due to the invasion of spliceosomal introns, which occurred during the evolution of Chlorophyceae. This finding provides concrete evidence supporting the "intron-late" model, which rests largely on the mobility of spliceosomal introns.
Amino Acid Sequence↗