Ishimizu T, Endo T, Yamaguchi-Kabata Y, Nakamura K T, Sakiyama F, Norioka S
Division of Protein Chemistry, Institute for Protein Research, Osaka University, Suita, Japan.
FEBS Lett. 1998 Dec 4;440(3):337-42. doi: 10.1016/s0014-5793(98)01470-7.
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.
花柱S-RNase与蔷薇科、茄科和玄参科的配子体自交不亲和性相关。这种S-RNase负责自交不亲和反应中的S等位基因特异性识别，但其在特异性识别中如何发挥作用尚不清楚。对蔷薇科S-RNase中同义替换数（dS）和非同义替换数（dN）的窗口分析检测到四个dN超过dS的区域，其中可能存在正选择作用（PS区域）。通过PHD方法预测的S-RNase二级结构拓扑与已知三级结构的真菌RNase Rh非常相似。当基于预测的二级结构将S-RNase的序列与RNase Rh的序列进行比对时，四个PS区域对应于RNase Rh三级结构上的两个表面位点。这些发现表明，在S-RNase中，PS区域也形成两个位点，并且是S等位基因特异性识别的识别位点候选者。
