CHARACTERIZATION OF A POLYMORPHIC FAMILY OF INTEGRAL MEMBRANE-PROTEINS IN PROMASTIGOTES OF DIFFERENT LEISHMANIA SPECIES

Antibodies raised against a Leishmania major recombinant promastigote surface antigen 2 (PSA-2) fragment recognized three major polypeptides of approximate M(r) 96 000, 80 000 and 50 000 in promastigotes of thr ee Israeli isolates of L. major including the cloned line LRC-L137-V12 1, but detected a different array of polypeptides in other L. major is olates. The pattern was different both in number of polypeptides detec ted and their molecular weight. The antibodies to L. major PSA-2 also recognized polypeptides in L. tropica, L. donovani and very weakly in L. mexicana promastigotes and in Crithidia lucilliae. The number and s ize of the polypeptides was different in each species. In addition to the membrane-bound PSA-2 polypeptides were identified water-soluble fo rms of PSA-2 released in promastigote culture supernatants. Peptide ma ps of the various L. major PSA-2 membrane polypeptides showed they wer e different from each other. N-terminal amino acid sequence of three p olypeptides expressed by L. major showed they are similar but distinct , consistent with being members of a polymorphic family. Because of th e extensive sequence similarity between the PSA-2 genes it has been di fficult to assign protein products to individual genes. As a first ste p towards solving this problem, we have transfected into L. mexicana a genomic clone of a L. major PSA-2 gene and shown that it produces a M (r) 35 000 polypeptide recognized by monoclonal and polyclonal antibod ies to L. major PSA-2.