title: Identification of regions in which positive selection may operate in S-RNase of Rosaceae: implication for S-allele-specific recognition sites in S-RNase.
abstract: A stylar S-RNase is associated with gametophytic self-incompatibility in the Rosaceae, Solanaceae, and Scrophulariaceae. This S-RNase is responsible for S-allele-specific recognition in the self-incompatible reaction, but how it functions in specific discrimination is not clear. Window analysis of the numbers of synonymous (dS) and non-synonymous (dN) substitutions in rosaceous S-RNases detected four regions with an excess of dN over dS in which positive selection may operate (PS regions). The topology of the secondary structure of the S-RNases predicted by the PHD method is very similar to that of fungal RNase Rh whose tertiary structure is known. When the sequences of S-RNases are aligned with the sequence of RNase Rh based on the predicted secondary structures, the four PS regions correspond to two surface sites on the tertiary structure of RNase Rh. These findings suggest that in S-RNases the PS regions also form two sites and are candidates for the recognition sites for S-allele-specific discrimination.
authors.affiliation: Division of Protein Chemistry, Institute for Protein Research, Osaka University, Suita, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Ishimizu
authors.forename: T
authors.initials: T
authors.lastname: Endo
authors.forename: Y
authors.initials: Y
authors.lastname: Yamaguchi-Kabata
authors.forename: K T
authors.initials: KT
authors.lastname: Nakamura
authors.forename: F
authors.initials: F
authors.lastname: Sakiyama
authors.forename: S
authors.initials: S
authors.lastname: Norioka
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012260:Ribonucleases / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D019685:Rosales / Q000201:enzymology / Q000235:genetics*; D012641:Selection, Genetic; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D012260:Ribonucleases; C022542:ribonuclease S