tailieunhanh - Báo cáo Y học: Identification of mammalian-type transglutaminase in Physarum polycephalum Evidence from the cDNA sequence and involvement of GTP in the regulation of transamidating activity

Transglutaminase (TGase) catalyses the post-translational modification of proteins by transamidation of available glutamine residues. While several TGase genes of fish and arthropods have been cloned and appear to have similar structures to those of mammals, no homologous gene has been found in lower eukaryotes. We have cloned the acellular slime mold Physarum polycephalum TGase cDNA using RT-PCR with degenerated primers, based on the partial amino acid sequence of the purified enzyme. The cDNA contained a 2565-bp ORF encoding a 855-residue polypeptide. By Northern blotting, an mRNA of 2600 bases was detected | Eur. J. Biochem. 269 3451- .util 22002 FEBS 2002 doi Identification of mammalian-type transglutaminase in Physarum polycephalum Evidence from the cDNA sequence and involvement of GTP in the regulation of transamidating activity Fumitaka Wada1 Akio Nakamura2 Tomohiro Masutani1. Koji Ikura3 Masatoshi Maki1 and Kiyotaka Hitomi1 1 Department of Applied Biological Sciences Graduate School of Bioagricultural Sciences Nagoya University Chikusa Nagoya Japan department of Pharmacology Gunma University School of Medicine Gunma Japan 3Department of Applied Biology Faculty of Textile Kyoto Institute of Technology Kyoto Japan Transglutaminase TGase catalyses the post-translational modification of proteins by transamidation of available glutamine residues. While several TGase genes of fish and arthropods have been cloned and appear to have similar structures to those of mammals no homologous gene has been found in lower eukaryotes. We have cloned the acellular slime mold Physarum polycephalum TGase cDNA using RT-PCR with degenerated primers basal nn the partial amino acid sequence of the purified enzyme. The cDNA contained a 2565-bp ORF encoding a 455-residue polypeptide. By Northern blotting nn mRNA of w2600 bases was detected. In comparison with primary sequences of mammalian TGases surprisingly significant similarity was observed including catalytic triad residues Cys HÍS Asn and a GTP-binding region. The alignment of sequences and a phylogenetic tree also demonstrated that the structure of P. polycephalum TGase is similar to that of TGases of vertebrates. Furthermore we observed that the purified TGase had GTP-hydrolysing activity and that GTP inhibited its transamidating activity as in the case of mam malian tissue-type TGase TGase 2 . Keywords GTP GTPase Physarum polycephalum transglutaminase. Transglutaminase TGase EC catalyses crosslinking between the y-carboxyamide of glutamine residues and the e-amino group of lysine residues .

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