Protein tyrosine phosphatases (PTPases) negatively regulae the effect(s) of protein tyrosine kinases and are implicated in the regulation of a variety of biological events including cell activation, differentiation, and neoplastic transformation. To gain insight into the role(s) of the PTPases, we mapped the gene encoding for the widely expressed receptor-like protein tyrosine phosphatase PTPα/LRP (locus symbol Ptpra) to rat chromosome 3q36 and mouse chromosome 2G by fluorescence in situ hybridization method. These results indicate that there is a conserved syntenic group between human 20p13, rat 3q36, and mouse 2G.
Four kinds of circular plasmid-like DNA, designated B1, B2, B3 and B4, have been found in the mitochondria of Oryza sativa L. with an AA genome. Three novel B1-homologous mitochondrial plasmid-like DNAs, designated, M1, M2 and M3, were isolated in the present study from strains with CC and CCDD genomes in the genus Oryza. We cloned and sequenced these DNAs and found that the sequences of these molecules have wide regions of homology. B1, M2 and M3 each lack about 300 bp of a region that is present in M1 and small repeats were found at the sites of deleted sequences. Therefore, we propose the hypothesis that the B1 family differentiated from a common ancient molecule that was similar to M1 via, probably, slipped mispairing during DNA replication at several stages in the evolution in the genus Oryza.
To estimate approximate times of divergence of animal phyla lacking fossil data, it is important to find a molecule that evolves with an approximately constant rate over a wide evolutionary distance covering the whole animal phyla. For this purpose, the evolutionary rate constancy has been examined for 20 proteins. It was found that four proteins, particularly the aldolase C, involved in the glycolitic pathway, had evolved with rates that are approximately constant not only among different classes of vertebrates, but also between vertebrates and arthropods. The evolutionary rate (= 0.26 × 10 -9/site/year) of the aldolase C is likely to have remained essentially unchanged even between animals and plants.