ANKYRIN AND BETA-SPECTRIN ACCUMULATE INDEPENDENTLY OF ALPHA-SPECTRIN IN DROSOPHILA

We report the identification and initial characterization of Drosophil a melanogaster ankyrin. Oligonucleotide printers based on the spectrin -binding domain of human brain ankyrin were used to amplify Drosophila genomic DNA. A cloned 184-bp PCR product was used to isolate Drosophi la ankyrin cDNAs. Ankyrin cDNA probes detected a 5.5-kb transcript fro m embryonic poly(A)(+) RNA and a single polytene chromosome locus (101 F-102A). The cDNA sequence encodes a 170-kDa protein that is 53% ident ical to human brain ankyrin (Ank2). Antibodies directed against a reco mbinant fragment of Drosophila ankyrin reacted with a 170-kDa polypept ide from Drosophila embryos, larvae, S2 cells, and adult flies. The an kyrin antibody coimmunoprecipitated alpha- and beta-spectrin with anky rin in detergent extracts of Drosophila embryo membranes. Antibodies a gainst Drosophila ankyrin, alpha-spectrin and beta-spectrin were used to detect these proteins in wild-type and alpha-spectrin-mutant larvae . alpha-Spectrin levels were greatly diminished in mutant larvae, but levels of ankyrin and beta-spectrin were indistinguishable from wild t ype. The persistence of ankyrin and beta-spectrin may explain the rela tively mild phenotype of alpha-spectrin mutants during early Drosophil a development.