ABC Transporters Involved in Export of Cell Surface Glycoconjugates
Tóm tắt
Complex glycoconjugates play critical roles in the biology of microorganisms. Despite the remarkable diversity in glycan structures and the bacteria that produce them, conserved themes are evident in the biosynthesis-export pathways. One of the primary pathways involves representatives of the ATP-binding cassette (ABC) transporter superfamily. These proteins are responsible for the export of a wide variety of cell surface oligo- and polysaccharides in both Gram-positive and Gram-negative bacteria. Recent investigations of the structure and function of ABC transporters involved in the export of lipopolysaccharide O antigens have revealed two fundamentally different strategies for coupling glycan polymerization to export. These mechanisms are distinguished by the presence (or absence) of characteristic nonreducing terminal modifications on the export substrates, which serve as chain termination and/or export signals, and by the presence (or absence) of a discrete substrate-binding domain in the nucleotide-binding domain polypeptide of the ABC transporter. A bioinformatic survey examining ABC exporters from known oligo- and polysaccharide biosynthesis loci identifies conserved nucleotide-binding domain protein families that correlate well with themes in the structures and assembly of glycans. The familial relationships among the ABC exporters generate hypotheses concerning the biosynthesis of structurally diverse oligo- and polysaccharides, which play important roles in the biology of bacteria with different lifestyles.
Từ khóa
Tài liệu tham khảo
Novotny, R., A. Pfoestl, P. Messner, and C. Schaffer. 2004. Genetic organization of chromosomal S-layer glycan biosynthesis loci of Bacillaceae. Glycoconj. J.20:435-447.
Ojeda, K. J., J. M. Box, and K. D. Noel. 2009. Genetic basis for Rhizobium etli CE3 O-antigen O-methylated residues that vary according to growth conditions. J. Bacteriol.192:679-690.
Silver, R. P., C. W. Finn, W. F. Vann, W. Aaronson, R. Schneerson, P. J. Kretschmer, and C. F. Garon. 1981. Molecular cloning of the K1 capsular polysaccharide genes of E. coli. Nature289:696-698.