VLPA OF VIBRIO-CHOLERAE-O1 - THE FIRST BACTERIAL MEMBER OF THE ALPHA(2)-MICROGLOBULIN LIPOCALIN SUPERFAMILY

We have identified a gene, vlpA, which is closely linked to the mfrA,B locus associated with mannose-fucose-resistant haemagglutination. Vlp A is an outer-membrane protein which can be labelled with [H-3]palmita te and whose processing is globomycin-sensitive, suggesting that it is a lipoprotein. Homology searches revealed that VlpA belongs to the gr oup of lipocalins of the alpha(2)-microglobulin superfamily which func tion as small hydrophobic molecule transporters, and is the first iden tified bacterial member of this group. Multiple copies of this gene ar e present in Vibrio cholerae 01 and 0139 and Southern hybridization re veals a biotype-specific pattern of fragment sizes. Construction of st rains capable of hyperproducing VlpA suggested that it is able to bind haemin with low affinity but this may be due to a simple hydrophobic interaction. Attempts to construct specific mutants in vlpA have been unsuccessful, presumably because of the multiple copies of vlpA genes and their linkage to the VCR element.