REPETITIVE ELEMENTS OF THE MYCOPLASMA-HOMINIS ADHESIN P50 CAN BE DIFFERENTIATED BY MONOCLONAL-ANTIBODIES

The gene encoding p50, an adhesin of Mycoplasma hominis, was identifie d, cloned, and sequenced. Comparison of the derived amino acid sequenc e with the N-terminal amino acids sequenced by the Edman reaction of t he native protein revealed that p50 is expressed as a 467-amino-acid p recursor. Posttranslational modification leads to a 441-amino-acid lip oprotein with an extended, predominantly helical structure and a leuci ne zipper. Computer analysis of the amino acid sequence identified a t hreefold-repetitive sequence motif comprising approximately three-quar ters of the total protein. Different regions of the p50 polypeptide ch ain were expressed in Escherichia coli. Western blot (immunoblot) anal ysis of the E. coli lysates revealed that the epitopes of four p50-spe cific monoclonal antibodies were localized in the middle and C-termina l part of the protein, Epitope mapping by exonuclease III digestion sh owed that all of the four monoclonal antibodies bound within the same region of the threefold-repetitive amino acid sequence motif. The repe ats, which were highly homologous but not identical in structure, coul d be differentiated by the monoclonal antibodies.