Characterisation of a second protein encoded by the differentially regulated LmcDNA16 gene family of Leishmania major.

The LmcDNA16 gene family of Leishmania major contains five genes: three highly related sequences, genes A, B and C, and a tandem pair of unrelated sequences, genes D1 and D2. Previous studies have demonstrated that gene B codes for a novel, hydrophilic protein that is present on the surface of infective parasite stages at approximately 10(5) copies per call. This paper describes the identification and characterisation of a second protein encoded by this gene array: the 7.6 kDa A/C protein. This molecule shares considerable amino acid identity with the gene B protein (GBP) but lacks the characteristic proline rich amino acid repeat region. Like GBP, the A/C protein is expressed on the surface of infective metacyclic parasites, despite the lack of conventional signal and anchor sequences. It has previously been suggested that the GBP repetitive sequence plays a role in mediating protein attachment to the parasite surface. It now appears more likely that the conserved amino- and/or carboxyl-terminal domains of the A/C and B proteins are involved in this process.