Publication Date:
2016-03-31
Description:
Capsular polysaccharides (CPSs), from Acinetobacter baumannii isolates 1432, 4190 and NIPH 70, which have related gene content at the K locus, were examined, and the chemical structures established using 2D 1 H and 13 C NMR spectroscopy. The three isolates produce the same pentasaccharide repeat unit, which consists of 5- N -acetyl-7- N -[( S )-3-hydroxybutanoyl] (major) or 5,7-di- N -acetyl (minor) derivatives of 5,7-diamino-3,5,7,9-tetradeoxy- d - glycero - d - galacto -non-2-ulosonic (legionaminic) acid (Leg5Ac7R), d -galactose, N -acetyl- d -galactosamine and N -acetyl- d -glucosamine. However, the linkage between repeat units in NIPH 70 was different to that in 1432 and 4190, and this significantly alters the CPS structure. The KL27 gene cluster in 4190 and KL44 gene cluster in NIPH 70 are organized identically and contain lga genes for Leg5Ac7R synthesis, genes for the synthesis of the common sugars, as well as an itrA2 initiating transferase and four glycosyltransferases genes. They share high-level nucleotide sequence identity for corresponding genes, but differ in the wzy gene encoding the Wzy polymerase. The Wzy proteins, which have different lengths and share no similarity, would form the unrelated linkages in the K27 and K44 structures. The linkages formed by the four shared glycosyltransferases were predicted by comparison with gene clusters that synthesize related structures. These findings unambiguously identify the linkages formed by Wzy K27 and Wzy K44 , and show that the presence of different wzy genes in otherwise closely related K gene clusters changes the structure of the CPS. This may affect its capacity as a protective barrier for A. baumannii .
Print ISSN:
0959-6658
Electronic ISSN:
1460-2423
Topics:
Biology
,
Medicine
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