Shibayama K, Ohsuka S, Tanaka T, Arakawa Y, Ohta M
Department of Bacteriology, School of Medicine, Nagoya University, Nagoya, 466-8550, Japan.
J Bacteriol. 1998 Oct;180(20):5313-8. doi: 10.1128/JB.180.20.5313-5318.1998.
Escherichia coli K-12 WaaO (formerly known as RfaI) is a nonprocessive alpha-1,3 glucosyltransferase, involved in the synthesis of the R core of lipopolysaccharide. By comparing the amino acid sequence of WaaO with those of 11 homologous alpha-glycosyltransferases, four strictly conserved regions, I, II, III, and IV, were identified. Since functionally related transferases are predicted to have a similar architecture in the catalytic sites, it is assumed that these four regions are directly involved in the formation of alpha-glycosidic linkage from alpha-linked nucleotide diphospho-sugar donor. Hydrophobic cluster analysis revealed a conserved domain at the N termini of these alpha-glycosyltransferases. This domain was similar to that previously reported for beta-glycosyltransferases. Thus, this domain is likely to be involved in the formation of beta-glycosidic linkage between the donor sugar and the enzyme at the first step of the reaction. Site-directed mutagenesis analysis of E. coli K-12 WaaO revealed four critical amino acid residues.
大肠杆菌K-12 WaaO（以前称为RfaI）是一种非持续性α-1,3葡糖基转移酶，参与脂多糖R核心的合成。通过将WaaO的氨基酸序列与11种同源α-糖基转移酶的序列进行比较，确定了四个严格保守的区域，即I、II、III和IV。由于功能相关的转移酶预计在催化位点具有相似的结构，因此假定这四个区域直接参与由α-连接的核苷酸二磷酸糖供体形成α-糖苷键。疏水簇分析揭示了这些α-糖基转移酶N末端的一个保守结构域。该结构域与先前报道的β-糖基转移酶的结构域相似。因此，该结构域可能在反应的第一步参与供体糖与酶之间β-糖苷键的形成。对大肠杆菌K-12 WaaO的定点诱变分析揭示了四个关键氨基酸残基。
