ESSENTIAL ROLE OF THE CONSENSUS NUCLEOTIDE-BINDING SITE OF PTLH IN SECRETION OF PERTUSSIS TOXIN FROM BORDETELLA-PERTUSSIS

PtlH is a member of a specialized set of transport proteins that is es sential for secretion of pertussis toxin (PT) from Bordetella pertussi s. Previously, PtlH was shown to contain a consensus nucleotide-bindin g motif. Here, we demonstrate that introduction of plasmids containing mutant forms of ptlH, altered in the putative nucleotide-binding regi on, into a wild-type strain of B. pertussis resulted in inhibition of PT secretion. Thus, this region of PtlH appears to be essential for pr otein function. Moreover, the observed dominant negative phenotype sug gests that PtlH either functions as a multimer or interacts with anoth er component necessary for secretion of PT.