We have isolated and characterized cDNA and genomic clones representing the calmodulin gene of Drosophila melanogaster. As demonstrated by genomic blots and by reconstruction experiments, the calmodulin gene is represented once in the Drosophila genome. In situ hybridization of cloned probes to the polytene chromosomes of third instar larvae permitted the localization of the gene to region 49A on the left arm of the second chromosome. Two transcripts of 1.65 and 1.9 kb are produced from this gene. The accumulation of calmodulin message was measured at several stages of Drosophila development. The results of these experiments suggest developmental regulation of the gene. Three intervening sequences interrupt the protein coding nucleotides and two of these are located within calmodulin functional domains. The DNA sequence encoding the protein is presented; the derived amino acid sequence is compared to that of other species. The structural similarities of the Drosophila calmodulin gene to calmodulin genes of other species and to other calcium binding protein genes are discussed.
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