Identification of genes coding for exported proteins of Actinobacillus actinomycetemcomitans

Random fusions of genomic DNA fragments to a partial gene encoding a signal sequence-deficient bacterial alkaline phosphatase were utilized to screen for exported proteins of Actinobacillus actinomycetemcomitans in Escherichi a coli. Twenty-four PhoA(+) clones were isolated and sequenced. Membrane lo calization signals in the form of signal sequences were deduced from most o f these sequences. Several of the deduced amino acid sequences were found t o be homologous to known exported or membrane-associated proteins. The comp lete genes corresponding to two of these sequences were isolated from an A. actinomycetemcomitans lambda phage library. One gene was found to be homol ogous to the outer membrane lipoprotein LolB. The second gene product had h omology with a Haemophilus influenzae protein and was localized to the inne r membrane of A. actinomycetemcomitans.