A 27.5-kb sequence that is present in an approx. 2-Mb chromosome in Leishmania also occurs as an inverted dimer in a multicopy, 55-kb circular molecule (LD1) in Leishmania infantum ITMAP263. Sequence analysis of a 7100-bp cloned segment from the circular molecule revealed three open reading frames (ORFs). The ORFs are likely to have protein coding function by a number of criteria, including Northern blot analyses. The amino acid (aa) sequences deduced from two ORFs showed no similarity to other sequences in the databases. The C-terminal aa sequence from the third ORF is related (22-29% identity, 57-71% similarity) to a family of genes conserved in bacteria and humans. One member (sfhB) of the gene family in Escherichia coli appears to have a role in regulation of cell growth.