Molecular characterization of the P1-like adhesin gene from Mycoplasma pirum.

A DNA fragment has been isolated from the genome of Mycoplasma pirum by use of a genetic probe derived from the conserved region within the genes for the major adhesins of Mycoplasma genitalium and Mycoplasma pneumoniae. A gene encoding an adhesin-like polypeptide was localized, and sequence analysis indicated a G + C content of only 28%, with A- and T-rich codons being preferentially used. A total of 91% of positions 3 were either A or T. The deduced polypeptide is 1,144 amino acids long (126 kDa) and shows 26% identity with the adhesins of M. genitalium and M. pneumoniae. Other features in common with these two membrane proteins include a similar hydropathic profile and a proline-rich C terminus. Antibodies were prepared by using as an immunogen a peptide derived from the C terminus of the M. pirum adhesin-like polypeptide and were found to recognize on immunoblots a 126-kDa polypeptide from an M. pirum cellular extract. The characterization of the adhesin-like gene is a first step toward a better understanding of the mechanisms allowing this human mycoplasma to attach to host cells.