title: Identification of an O-acyltransferase gene (oacB) that mediates 3- and 4-O-acetylation of rhamnose III in Shigella flexneri O antigens.
abstract: O antigen (O polysaccharide) is an important and highly variable cell component present on the surface of cells which defines the serospecificity of Gram-negative bacteria. Most O antigens of Shigella flexneri, a cause of shigellosis, share a backbone composed of →2)-α-l-Rhap(III)-(1→2)-α-l-Rhap(II)-(1→3)-α-l-Rhap(I)-(1→3)-β-d-GlcpNAc-(1→ repeats, which can be modified by adding various substituents, giving rise to 19 serotypes. The known modifications include glucosylation on various sugar residues, O-acetylation on Rha(I), and phosphorylation with phosphoethanolamine on Rha(II) or/and Rha(III). Recently, two new O-antigen modifications, namely, O-acetylation at position 3 or 4 of Rha(III) and position 6 of GlcNAc, have been identified in several S. flexneri serotypes. In this work, the genetic basis for the 3/4-O-acetylation on Rha(III) was elucidated. Bioinformatic analysis of the genome of S. flexneri serotype 2a strain Sf301, which carries 3/4-O-acetylation on Rha(III), revealed an O-acyltransferase gene designated oacB. Genetic studies combined with O-antigen structure analysis demonstrated that this gene is responsible for the 3/4-O-acetylation in serotypes 1a, 1b, 2a, 5a, and Y but not serotype 6, which has a different O-antigen backbone structure. The oacB gene is carried by a transposon-like structure located in the proA-adrA region on the chromosome, which represents a novel mechanism of mobilization of O-antigen modification factors in S. flexneri. These findings enhance our knowledge of S. flexneri O-antigen modifications and shed light on the origin of new O-antigen variants.
authors: State Key Laboratory for Infectious Disease Prevention and Control, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, National Institute for Communicable Disease Control and Prevention, China CDC, Changping, Beijing, China.
authors: Jianping
authors: J
authors: Wang
authors: Yuriy A
authors: YA
authors: Knirel
authors: Ruiting
authors: R
authors: Lan
authors: Sof'ya N
authors: SN
authors: Senchenkova
authors: Xia
authors: X
authors: Luo
authors: Andrei V
authors: AV
authors: Perepelov
authors: Yiting
authors: Y
authors: Wang
authors: Alexander S
authors: AS
authors: Shashkov
authors: Jianguo
authors: J
authors: Xu
authors: Qiangzheng
authors: Q
authors: Sun
mesh_terms: D000107:Acetylation; D000217:Acyltransferases / Q000235:genetics* / Q000378:metabolism*; D002240:Carbohydrate Sequence; D019295:Computational Biology; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D019081:O Antigens / Q000737:chemistry / Q000378:metabolism*; D012210:Rhamnose / Q000378:metabolism*; D012703:Serotyping; D012763:Shigella flexneri / Q000201:enzymology* / Q000235:genetics*
chemical_list: D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D019081:O Antigens; D000217:Acyltransferases; D012210:Rhamnose