The gene encoding the metacyclogenesis-associated transcript Mat-1 is conserved in the genus Leishmania and shows a tendency to form dimers upon protein expression.

The Leishmania infantum Mat-1 gene--recently described in L. major as a highly stage-specific, metacyclogenesis-associated transcript--has been cloned. The 420-bp Mat-1 coding region is conserved with respect to the L. major gene (82% sequence homology). Analysis of the predicted amino-acid sequence reveals structural motifs showing homology with the class of leucine-zipper transcription factors. Southern-blot hybridization analysis suggests that Mat-1 is a low-copy-number gene, probably consisting of two gene copies. The recombinant Mat-1 protein expressed in fusion with the Escherichia coli maltose-binding protein shows a tendency to form dimers in the presence of the leucine-rich C-terminal domain. Bacteria expressing the Mat-1 open reading frame are highly growth-attenuated and tend to delete or modify the insert, which suggests that expression of Mat-1 is toxic for the bacteria.