Calphotin: a drosophila photoreceptor cell calcium-binding protein

• Published in: Proceedings of the National Academy of Sciences - PNAS 1993-02, Vol.90 (4), p.1531-1535
• Main Authors: Martin, J.H. (University of Southern California School of Medicine, Los Angeles, CA), Benzer, S, Rudnicka, M, Miller, C.A
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino acids; Analytical, structural and metabolic biochemistry; Animals; Antibodies, Monoclonal; ANTICORPS MONOCLONAL; ANTICUERPOS MONOCLONALES; Antigens; Base Sequence; Binding and carrier proteins; Biological and medical sciences; Biology; Blotting, Northern; CALCIO; CALCIUM; Calcium - metabolism; calcium-binding protein; Calcium-Binding Proteins - analysis; Calcium-Binding Proteins - genetics; Calcium-Binding Proteins - metabolism; calphotin; cDNA; chromosome 3; CODE GENETIQUE; CODIGO GENETICO; Complementary DNA; Compound eyes; Databases, Factual; Drosophila; DROSOPHILA MELANOGASTER; Drosophila melanogaster - physiology; Drosophila Proteins; EXPRESION GENICA; EXPRESSION DES GENES; Eyes & eyesight; Fundamental and applied biological sciences. Psychology; Gene Library; genes; Immunoblotting; In Situ Hybridization; Insect Hormones - genetics; Insect Hormones - metabolism; Insect Proteins; Insects; Leucine Zippers - genetics; mapping; Messenger RNA; Microscopy, Electron; Molecular Sequence Data; nucleotide sequence; Ocelli; OEIL; OJOS; ORGANE DES SENS; ORGANOS SENSORIALES; Photoreceptor Cells - metabolism; Photoreceptor Cells - ultrastructure; Photoreceptors; Poly A - analysis; Poly A - genetics; Poly A - metabolism; predictions; PROTEINAS; PROTEINE; Proteins; RNA, Messenger - analysis; RNA, Messenger - genetics; RNA, Messenger - metabolism; SECUENCIA NUCLEICA; SEQUENCE NUCLEIQUE
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.90.4.1531

Monoclonal antibody 23E9 identifies a calcium-binding protein, calphotin, in photoreceptor cells of the Drosophila melanogaster compound eyes and ocelli. The antigen is restricted to a defined cytoplasmic region; it is not present in the rhabdomeres, nuclei, mitochondria, or rough endoplasmic reticulum. A corresponding cDNA recognizes a 3-kb mRNA with retinal specificity similar to the antigen and maps to band 86E/F-87A/B on chromosome 3. An open reading frame of 2595 bp encodes an estimated 85-kDa protein of unusual amino acid composition, with 50% proline, alanine, and valine and very few basic residues. The C-terminal segment contains a leucine zipper motif uninterrupted by prolines. We found no significant similarities with the GenBank or National Biomedical Resource Foundation data bases. The location of the protein within a distinct cytoplasmic region suggests that it might function as a calcium-sequestering "sponge" to regulate the amount of free cytoplasmic calcium