A 135-KILODALTON SURFACE-ANTIGEN OF MYCOPLASMA-HOMINIS PG21 CONTAINS MULTIPLE DIRECTLY REPEATED SEQUENCES

A monoclonal antibody was used to characterize a 135-kDa surface-locat ed membrane protein (Lmp1) generally present in Mycoplasma hominis str ains. The monoclonal antibody, 552, was applied to identify the corres ponding gene in an expression library of M. hominis PG21 DNA. The M. h ominis PG21 lmp1 gene was sequenced, and its gene product was characte rized with the goal of elucidating the structure and function of Lmp1. A total of 7,196 bp in the lmp1 region was sequenced. An open reading frame of 4,032 bp, encoding a protein of 1,344 amino acids with a cal culated molecular weight of 147,000, was identified. Analysis of the d educed amino acid sequence predicted a hydrophilic protein with a basi c pI (10.0). The N terminal 24 amino acids were a tqpical leader seque nce. Downstream from the first 726 nucleotides, six similar direct rep eats of 471 nucleotides were found. In repeat 7, a single-base substit ution, C-->A, gave rise to the stop codon of lmp1. Thus, the C-termina l 935 amino acids were encoded by the 471-bp direct repeats. As eviden ced by Southern blot analysis, the gene encoding the 135-kDa antigen i s part of a multigene family. One of the genes, lmp2, was situated dir ectly downstream from lmp1 where the direct repeats continued,