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Journal of Bacteriology, November 2006, p. 7542-7550, Vol. 188, No. 21
0021-9193/06/$08.00+0     doi:10.1128/JB.00783-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

O Acetylation of the Enterobacterial Common Antigen Polysaccharide Is Catalyzed by the Product of the yiaH Gene of Escherichia coli K-12

Junko Kajimura,^1, Arifur Rahman,¹ James Hsu,¹ Matthew R. Evans,² Kevin H. Gardner,² and Paul D. Rick^1*

Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814-4799,¹ Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390-8816²

Received 31 May 2006/ Accepted 15 August 2006

The carbohydrate component of the enterobacterial common antigen (ECA) of Escherichia coli K-12 occurs primarily as a water-soluble cyclic polysaccharide located in the periplasm (ECA_CYC) and as a phosphoglyceride-linked linear polysaccharide located on the cell surface (ECA_PG). The polysaccharides of both forms are comprised of the amino sugars N-acetyl-D-glucosamine (GlcNAc), N-acetyl-D-mannosaminuronic acid (ManNAcA), and 4-acetamido-4,6-dideoxy-D-galactose (Fuc4NAc). These amino sugars are linked to one another to form trisaccharide repeat units with the structure 3--D-Fuc4NAc-(14)-ß-D-ManNAcA-(14)--D-GlcNAc-(1. The hydroxyl group in the 6 position of the GlcNAc residues of both ECA_CYC and ECA_PG are nonstoichiometrically esterified with acetyl groups. Random transposon insertion mutagenesis of E. coli K-12 resulted in the generation of a mutant defective in the incorporation of O-acetyl groups into both ECA_CYC and ECA_PG. This defect was found to be due to an insertion of the transposon into the yiaH locus, a putative gene of unknown function located at 80.26 min on the E. coli chromosomal map. Bioinformatic analyses of the predicted yiaH gene product indicate that it is an integral inner membrane protein that is a member of an acyltransferase family of enzymes found in a wide variety of organisms. The results of biochemical and genetic experiments presented here strongly support the conclusion that yiaH encodes the O-acetyltransferase responsible for the incorporation of O-acetyl groups into both ECA_CYC and ECA_PG. Accordingly, we propose that this gene be designated wecH.

Published ahead of print on 25 August 2006.

Present address: Department of Experimental Oncology, University of Hiroshima, Research Institute for Radiation Biology and Medicine, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan.