Localization of Drosophila retinal degeneration B, a membrane-associated phosphatidylinositol transfer protein.
The Drosophila retinal degeneration B (rdgB) mutation causes abnormal photoreceptor response and light-enhanced retinal degeneration. Immunoblots using polyclonal anti-rdgB serum showed that rdgB is a 160-kD membrane protein. The antiserum localized the rdgB protein in photoreceptors, antennae, and regions of the Drosophila brain, indicating that the rdgB protein functions in many sensory and neuronal cells. In photoreceptors, the protein localized adjacent to the rhabdomeres, in the vicinity of the subrhabdomeric cisternae. The rdgB protein's amino-terminal 281 residues are > 40% identical to the rat brain phosphatidylinositol transfer protein (PI-TP). A truncated rdgB protein, which contains only this amino-terminal domain, possesses a phosphatidylinositol transfer activity in vitro. The remaining 773 carboxyl terminal amino acids have additional functional domains. Nitrocellulose overlay experiments reveal that an acidic amino acid domain, adjacent to the PI transfer domain, binds 45Ca+2. Six hydrophobic segments are found in the middle of the putative translation product and likely function as membrane spanning domains. These results suggest that the rdgB protein, unlike the small soluble PI-TPs, is a membrane-associated PI-TP, which may be directly regulated by light-induced changes in intracellular calcium.
Vihtelic
T S
TS
Department of Biological Sciences, University of Notre Dame, Indiana 46556.
Goebl
M
M
Milligan
S
S
O'Tousa
J E
JE
Hyde
D R
DR
D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001692:Biological Transport / Q000502:physiology; D015153:Blotting, Western; D001923:Brain Chemistry; D002118:Calcium / Q000378:metabolism; D002132:Calcium Radioisotopes; D002352:Carrier Proteins / Q000032:analysis* / Q000235:genetics / Q000502:physiology; D002462:Cell Membrane / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure; D004247:DNA / Q000378:metabolism; D004330:Drosophila; D029721:Drosophila Proteins; D005136:Eye Proteins; D015870:Gene Expression; D005796:Genes / Q000235:genetics; D007150:Immunohistochemistry; D008027:Light; D008565:Membrane Proteins / Q000032:analysis* / Q000235:genetics / Q000502:physiology; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009154:Mutation / Q000235:genetics; D009475:Neurons, Afferent / Q000737:chemistry / Q000166:cytology / Q000502:physiology; D049294:Phospholipid Transfer Proteins; D010743:Phospholipids / Q000378:metabolism; D010786:Photoreceptor Cells / Q000737:chemistry / Q000166:cytology / Q000502:physiology; D012162:Retinal Degeneration / Q000503:physiopathology
D002132:Calcium Radioisotopes; D002352:Carrier Proteins; D029721:Drosophila Proteins; D005136:Eye Proteins; D008565:Membrane Proteins; D049294:Phospholipid Transfer Proteins; D010743:Phospholipids; C068848:rdgB protein, Drosophila; D004247:DNA; D002118:Calcium