title: On a salmon (Oncorhynchus [corrected] keta) liver RNase, belonging to RNase T2 family: primary structure and some properties.
abstract: A base-nonspecific and acid ribonuclease (RNase Ok2) was purified from the liver of a salmon (Oncorhnchus keta) to a homogeneous state by SDS-PAGE. The primary structure of RNase Ok2 was determined by protein chemistry and molecular cloning. The RNase Ok2 was a glycoprotein and consisted of 216 amino acid residues. Its molecular mass of protein moiety was 25,198, and its amino acid sequence showed that it belongs to the RNase T2 family of enzymes. The optimal pH of RNase Ok2 was around 5.5. The base preferences at the B1 and B2 sites were estimated from the rates of hydrolysis of 16 dinucleoside phosphates to be G>>A>U, C, and G>A>U>C respectively. In this enzyme, one of the three histidine residues which have been thought to be important for catalysis of RNase Rh, a typical RNase of this family of enzymes, His104 was replaced by tyrosine residue. Based on the results, the role of H104, which has been proposed to be a phosphate binding site with a substrate, was reconsidered, and we proposed a revised role of this His residue in the hydrolysis mechanism of RNase T2 family enzymes.
authors.affiliation: Department of Applied Microbiology, Hoshi University, Tokyo, Japan.
authors.forename: Rie
authors.initials: R
authors.lastname: Suzuki
authors.forename: Sachiko
authors.initials: S
authors.lastname: Kanno
authors.forename: Yuko
authors.initials: Y
authors.lastname: Ogawa
authors.forename: Masanori
authors.initials: M
authors.lastname: Iwama
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Tsuji
authors.forename: Kazuko
authors.initials: K
authors.lastname: Ohgi
authors.forename: Masachika
authors.initials: M
authors.lastname: Irie
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004722:Endoribonucleases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli; D015870:Gene Expression; D008099:Liver / Q000201:enzymology*; D008969:Molecular Sequence Data; D017685:Oncorhynchus keta / Q000378:metabolism*; D030781:Organisms, Genetically Modified; D010802:Phylogeny; D012441:Saccharomyces cerevisiae; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D004722:Endoribonucleases; C022543:ribonuclease T(2)