Sequence heterogeneity and polymorphic gene arrangements of the Leishmania guyanensis gp63 genes

The Leishmania GP63 major surface protein gene family encodes multiple isoforms which differ predominantly in the carboxyterminal region. We have isolated 4 full-length gp63 cDNA clones derived from stationary-phase promastigote RNA of a cloned isolate of Leishmania guyanensis, a member of the braziliensis complex. These genes, along with the previously published L. guyanensis gp63 gene sequence [15], appeared to be mosaics of different combinations of 5' and 3' untranslated regions and sequences encoding the propeptide, internal, and C-terminal regions of GP63. The predicted L. guyanensis GP63 isoforms shared as little as 55% sequence identity, comparable to the inter-species diversity of GP63. The genomic organization of gp63 genes in L. guyanensis is highly complex: there are at least 4 distinct polymorphic forms of tandemly linked gene clusters, with intra-gene cluster variation in gene sequence and in the number of gene repeats. Southern blot analysis suggested that the arrangement of gp63 genes in this L. guyanensis isolate did not differ from that in the parental lines.