title: Cloning and characterization of dihydrofolate reductases from deep-sea bacteria.
abstract: Enzymes from organisms living in deep-sea are thought to have characteristic pressure-adaptation mechanisms in structure and function. To better understand these mechanisms in dihydrofolate reductase (DHFR), an essential enzyme in living cells, we cloned, overexpressed and purified four new DHFRs from the deep-sea bacteria Shewanella violacea (svDHFR), Photobacterium profundum (ppDHFR), Moritella yayanosii (myDHFR) and Moritella japonica (mjDHFR), and compared their structure and function with those of Escherichia coli DHFR (ecDHFR). These deep-sea DHFRs showed 33-56% primary structure identity to ecDHFR while far-ultraviolet circular dichroism and fluorescence spectra suggested that their secondary and tertiary structures were not largely different. The optimal temperature and pH for deep-sea DHFRs activity were lower than those of ecDHFR and different from each other. Deep-sea DHFRs kinetic parameters K(m) and k(cat) were larger than those of ecDHFR, resulting in 1.5-2.8-fold increase of k(cat)/K(m) except for mjDHFR which had a 28-fold decrease. The enzyme activity of ppDHFR and mjDHFR (moderate piezophilic bacteria) as well as ecDHFR decreased as pressure increased, while svDHFR and myDHFR (piezophilic bacteria) showed a significant tolerance to pressure. These results suggest that DHFRs from deep-sea bacteria possess specific enzymatic properties adapted to their life under high pressure.
authors.affiliation: Department of Mathematical and Life Sciences, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Japan.
authors.forename: Chiho
authors.initials: C
authors.lastname: Murakami
authors.forename: Eiji
authors.initials: E
authors.lastname: Ohmae
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Tate
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Gekko
authors.forename: Kaoru
authors.initials: K
authors.lastname: Nakasone
authors.forename: Chiaki
authors.initials: C
authors.lastname: Kato
mesh_terms: D000220:Adaptation, Biological; D000595:Amino Acid Sequence; D001274:Atmospheric Pressure; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D005798:Genes, Bacterial; D006092:Gram-Negative Facultatively Anaerobic Rods / Q000201:enzymology* / Q000235:genetics*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008969:Molecular Sequence Data; D034221:Moritella / Q000201:enzymology / Q000235:genetics; D009792:Oceans and Seas; D010776:Photobacterium / Q000201:enzymology / Q000235:genetics; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D012623:Seawater / Q000382:microbiology*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D020592:Shewanella / Q000201:enzymology / Q000235:genetics; D013696:Temperature; D013762:Tetrahydrofolate Dehydrogenase / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D011993:Recombinant Fusion Proteins; D013762:Tetrahydrofolate Dehydrogenase