RELATEDNESS AND PHYLOGENY WITHIN THE FAMILY OF PERIPLASMIC CHAPERONESINVOLVED IN THE ASSEMBLY OF PILI OR CAPSULE-LIKE STRUCTURES OF GRAM-NEGATIVE BACTERIA

The structure of a Salmonella enterica serovar typhi gene located with in the fim gene cluster and encoding a putative periplasmic chaperone- like protein involved in the assembly of type 1 pili was determined. T his gene, named fimC, has the ability to encode a 26-kDa polypeptide w hich is similar, at the sequence level, to the PapD periplasmic chaper onin mediating the assembly of P pili of Escherichia coli, as well as to other periplasmic chaperone-like proteins involved in the biogenesi s of pill or capsule-like structures of various Gram-negative bacteria . A comprehensive search through the literature and sequence databases identified 31 (putative) bacterial proteins that can be included in t his protein family on the basis of sequence similarity. Results of a m ultiple sequence comparison analysis showed that several residues, inc luding most of those known to be critical in maintaining the three-dim ensional structure of PapD, are either conserved or conservatively sub stituted in all these proteins, suggesting an overall similar folding for all of them. It was also evident that members of this family are c lustered into different subfamilies according to structural and phylet ic data.