Abstract
We have isolated a cDNA clone (λIRBP-1) for bovine interphotoreceptor retinoid-binding protein (IRBP) by immunological screening of a bovine retinal λgt11 cDNA expression library. This clone contained a cDNA insert 325 bp in length. A 250 bp fragment of this cDNA was used to screen a bovine retina λgt10 cDNA library, resulting in the isolation of two larger cDNA clones containing inserts of 2.5 kb (λIRBP-2) and 1.5 kb (λIRBP-3). Restriction endonuclease mapping revealed all three clones to have an EcoR I restriction site. The 250 bp fragment of λIRBP-1 and the 2000 bp fragment of λIRBP-2 both hybridized to a single bovine retinal mRNA species approximately 8 kb in length; there was no hybridization with either chicken lens or liver RNA. The amino acid sequence of a tryptic peptide from authentic IRBP has been obtained. The deduced amino acid sequence from the cDNA nucleotide sequence is the same as this authentic peptide. This definitively establishes the identity of the cDNA clones as encoding bovine IRBP.