A novel, testis-specific member of the cellular lipophilic transport protein superfamily, deduced from a complimentary deoxyribonucleic acid clone.
A novel member of the cellular lipophilic transport protein superfamily was identified after an antiserum raised against cellular retinoic acid-binding protein (CRABP) was found also to contain antibodies against another 15-kDa protein present in the cytosol of pubertal and adult rat testis. These antibodies were used to screen a rat testis cDNA expression library and isolate a 561-bp clone containing a full open reading frame from which the sequence of a novel 132 amino acid protein was deduced. The protein has 58% amino acid sequence identity to bovine myelin P2, 58% identity to murine adipocyte lipid-binding protein, and 40% identity to rat CRABP. Although the endogenous ligand has not yet been identified, conservation of residues involved in the binding of carboxylate groups suggests that the ligand is a fatty acid or an acidic retinoid. Tissue-specific expression was examined by Northern analysis and immunolocalization and appears to be restricted to late germ cells within the testis and epididymis. Immunostaining was first detectable in mid-pachytene spermatocytes and increased in intensity as these cells progressed to elongated spermatids, suggesting that this testis lipid-binding protein has a specific role in sperm development.
Schmitt
M C
MC
Department of Biochemistry, Vanderbilt University, Nashville, Tennessee 37232.
Jamison
R S
RS
Orgebin-Crist
M C
MC
Ong
D E
DE
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D002417:Cattle; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics*; D007150:Immunohistochemistry; D050356:Lipid Metabolism; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D051381:Rats; D017207:Rats, Sprague-Dawley; D018168:Receptors, Retinoic Acid / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013737:Testis / Q000378:metabolism*
D002352:Carrier Proteins; D018076:DNA, Complementary; D018168:Receptors, Retinoic Acid