Conserved Structural Regions Involved in the Catalytic Mechanism of Escherichia coli K-12 WaaO (RfaI) |
| |
Authors: | Keigo Shibayama Shinji Ohsuka Toshihiko Tanaka Yoshichika Arakawa and Michio Ohta |
| |
Institution: | Department of Bacteriology, School of Medicine, Nagoya University, Nagoya, 466-8550,1. and Department of Bacterial and Blood Products, National Institute of Infectious Diseases, Tokyo, 208-0011,2. Japan |
| |
Abstract: | Escherichia coli K-12 WaaO (formerly known as RfaI) is a nonprocessive α-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 α-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 α-glycosidic linkage from α-linked nucleotide diphospho-sugar donor. Hydrophobic cluster analysis revealed a conserved domain at the N termini of these α-glycosyltransferases. This domain was similar to that previously reported for β-glycosyltransferases. Thus, this domain is likely to be involved in the formation of β-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. |
| |
Keywords: | |
|
|