Cloning and molecular characterization of a voltage-dependent anion-selective channel (VDAC) from Drosophila melanogaster

A full length voltage-dependent anion-selective channel (VDAC) cDNA was cloned from Drosophila melanogaster by expression library screening using an antibody against an insect VDAC protein. The cDNA clone (denoted DmVDAC) is 1082 base pairs (bp) in length and contains an open reading frame (bp 62-907) encoding a 282 amino acid protein which has a predicted molecular mass of 30 550 Da, a predicted pI of 6.98 and no cysteines. Hydrophobicity analysis suggests 15 or 16 membrane-spanning domains. The DmVDAC amino acid sequence has variable homology with VDACs from other species ranging from 62% identity with a human VDAC to 23% identity with a Dictyostelium discoideum VDAC. DmVDAC has 92% identity with the 38 conserved residues in a VDAC consensus sequence. DmVDAC was expressed in VDAC-null yeast but failed to rescue viability. DmVDAC has 88% identity at the amino acid level and 99% identity at the nucleic acid level with a recently reported D. melanogaster VDAC sequence (A. Messina et al., FEBS Lett. 384 (1996) 9-13). Homology analyses with the Messina and other VDAC sequences indicate that the amino acid differences are due to minor errors in the Messina sequence, Southern blots and chromosomal in situ hybridizations suggest a single VDAC gene occurs in the fly with a locus at 32B on the left arm of the second chromosome.