The fruit fly Drosophila melanogaster has been extensively used to identify genes required for photoreceptor cell function. We show that the ninaC gene, originally isolated as a Drosophila visual mutation with an electrophysiological phenotype, encodes two novel cytoskeletal proteins. We identified the DNA sequences encoding the ninaC gene by rescuing the electrophysiological phenotype using P-element-mediated germ line transformation. The ninaC locus is expressed as two extensively overlapping mRNAs encoding proteins of 1135 and 1501 amino acids. Both proteins contain a putative protein kinase domain joined to a domain homologous to the head region of the myosin heavy chain and are spatially restricted to photoreceptor cells.