Analysis of the genomic organisation of a small chromosome of Leishmania braziliensis M2903 reveals two genes encoding GTP-binding proteins, one of which belongs to a new G-protein family and is an antigen.

Leishmania braziliensis M2903 contains a highly amplified small chromosome. This work is aimed at resolving its structural organization and determining whether this unusual chromosome contains specific genes encoding proteins with important functions in disease pathology or drug resistance. Our results show that the M2903 250-kb small chromosome contains LD1 sequences and has an inverted repeat structure. The LD1 sequences and two cDNAs (cDNA2 and cDNA53) were mapped on a cosmid contig, and the two cDNAs and the corresponding genomic fragments from the small chromosome were sequenced. The gene encoding cDNA2 predicts a putative GTP-binding protein with homology to other GTP-binding proteins only in the G-1 domain region; however, four other conserved motifs can be recognized. Sequence similarity to cDNA53 is located in at least five chromosomes, and its small chromosome copy is a pseudogene. An open reading frame downstream of the cDNA53 pseudogene predicts another GTP-binding protein that belongs to a new G-protein family with an unusual conserved GTP-binding domain and a newly characterized conserved sequence motif. A portion of this GTP-binding protein gene was studied previously in L. aethiopica as a recombinant antigen that reacts with human antibodies.

Genomic DNA repeat from Leishmania (Viannia) braziliensis (Venezuelan strain) containing simple repeats and microsatellites.

In this paper the Leishmania (Viannia) braziliensis complex is defined as containing all species of the actual subgenus Viannia. Organisms of the L. (V) braziliensis complex are the causative agents of localized human cutaneous and mucocutaneous leishmaniasis in South America, much of Central America and some ares of North America. In our search for better species and subspecies diagnostic probes we focused our research on repetitive DNA, since it provides a greater number of target sites for hybridization. In this work we report the isolation and sequencing of a 1.8 kb DNA region, LbJ38, which is probably tandemly repeated or dispersed at least 4 times along one chromosome and is naturally present in L. (V) braziliensis genomic DNA. This region contains microsatellites and simple repeat DNA sequences and was isolated by screening a genomic DNA cosmid library with complex- and species-specific probes. No homology was found with other Leishmania microsatellite or repetitive DNA. The utility of this repetitive sequence and primers derived from it in the identification of L. (V) braziliensis is demonstrated. As far as we are aware, this is the first report of sequence characterized repetitive microsatellite and GC rich simple repeat DNA from the nuclear genome of New World Leishmania.