MULTIPLE FORMS OF DYNAMIN ARE ENCODED BY SHIBIRE, A DROSOPHILA GENE INVOLVED IN ENDOCYTOSIS

DYNAMIN was discovered in bovine brain tissue as a nucleotide-sensitive microtubule-binding protein of relative molecular mass 100,000 1. It was found to cross-link microtubules into highly ordered bundles, and appeared to have a role in intermicrotubule sliding in vitro. Cloning and sequencing of rat brain dynamin complementary DNA identified an N-terminal region of about 300 amino acids which contained the three consensus elements characteristic of GTP-binding proteins 2. Extensive homology was found between this domain and the mammalian Mx proteins which are involved in interferon-induced viral resistance 3,4, and with the product of the VPS1 locus in Saccharomyces cerevisiae, which has been implicated both in membrane protein sorting 5, and in meiotic spindle pole separation 6. Dynamin-containing microtubule bundles were not observed in an immunofluorescence study of cultured mammalian cells 7, but a role for a GTP-requiring protein in intermicrotubule sliding during mitosis in plants has been reported 8. We report here that Drosophila melanogaster contains multiple tissue-specific and developmentally-regulated forms of dynamin, which are products of the shibire locus previously implicated in endocytic protein sorting 9,10.