Cloning and tissue localization of a novel zebrafish RdgB homolog that lacks a phospholipid transfer domain.
The retinal degeneration B (RdgB) protein family is characterized by an amino-terminal phosphatidylinositol transfer protein (PITP) domain, several hydrophobic domains, and a highly conserved carboxyl terminus. We identified a zebrafish RdgB homolog (pl-RdgB) that lacks the amino-terminal PITP domain, while retaining over 45% amino acid identity with the two mouse RdgB proteins (M-RdgB1 and M-RdgB2). Unlike the widespread retinal expression observed for other vertebrate RdgB homologs, pl-RdgB is restricted in the retina to the cone cell inner segments. The pl-RdgB protein is also expressed in the brain, although its distribution is different than the other RdgB homologs. Analogous to M-RdgB2, pl-RdgB protein is extracted from a retinal homogenate by guanidine and not by Triton X-100. Thus, pl-RdgB and likely all the identified RdgB homologs are not integral membrane proteins, but may associate with the membrane through protein-protein interactions. While expression of either murine RdgB homolog restored the defective light response and prevented retinal degeneration in rdgB mutant flies, expressing zebrafish pl-RdgB in Drosophila rdgB2 null mutants slowed retinal degeneration without restoring the electrophysiological light response. Thus, pl-RdgB may define a previously unrecognized protein family, which includes the other RdgB homologs, that act through a protein complex to maintain photoreceptor viability.
Elagin
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VA
Department of Biological Sciences, University of Notre Dame, IN 46556-0369, USA.
Elagina
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RB
Doro
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CJ
Vihtelic
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Hyde
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D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D017931:DNA Primers / Q000737:chemistry; D004330:Drosophila / Q000235:genetics; D029721:Drosophila Proteins; D004596:Electroretinography; D005136:Eye Proteins; D019084:Fluorescent Antibody Technique, Indirect; D015870:Gene Expression; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D049294:Phospholipid Transfer Proteins; D010743:Phospholipids / Q000378:metabolism*; D012160:Retina / Q000378:metabolism*; D012162:Retinal Degeneration / Q000235:genetics* / Q000378:metabolism / Q000517:prevention & control; D017386:Sequence Homology, Amino Acid; D015027:Zebrafish
D002352:Carrier Proteins; D017931:DNA Primers; D029721:Drosophila Proteins; D005136:Eye Proteins; D008565:Membrane Proteins; D049294:Phospholipid Transfer Proteins; D010743:Phospholipids; C068848:rdgB protein, Drosophila