CHARACTERIZATION OF THE GENE ENCODING THE IRON-SULFUR PROTEIN SUBUNITOF SUCCINATE-DEHYDROGENASE FROM DROSOPHILA-MELANOGASTER

The iron-sulfur protein (Ip) subunit of succinate dehydrogenase (and c omplex II of the electron transport chain) is highly conserved in evol ution [Gould et al., Proc. Natl. Acad. Sci. USA 86 (1989) 1934-1938]. We have cloned the Drosophila melanogaster Ip-encoding gene (SdhB) by genomic library screening using the human Ip-encoding cDNA as a probe at low stringency. A 2.7-kb fragment containing SdhB has been sequence d and shown to comprise the entire transcribed region and more than 90 0 bp of promoter region. The gene contains three exons and two small i ntrons of 272 and 56 nt, respectively, and is transcribed into an mRNA of 1205 nt (plus poly(A) tail). The deduced amino-acid (aa) sequence shows strong similarities with Ip peptides from Escherichia coli, yeas ts, plants and mammals, with 100% aa identity around the three Cys clu sters which form the non-heme iron-sulfur centers. In situ hybridizati on on polytene chromosomes maps SdhB to band 42D 1-5 on the right arm of the second chromosome next to the centromere. Developmental and tis sue-specific Northern blots show a single transcript of 1.3 kb in all tissues. However, its abundance varies during development and in the m ajor body segments of the adult fly. Pupae have very low levels of tra nscript, in contrast to larvae. It is most abundant in the adult thora x and low in abdominal tissues.