NUCLEOTIDE-SEQUENCE OF THE CANINE ROD-OPSIN-ENCODING GENE

The major parts of two canine rod-specific opsin (Ops) transcripts hav e been cloned by polymerase chain reaction from retinal mRNA. Both tra nscripts are derived from the same gene. The 5' leader sequence of the transcripts was cloned from canine peripheral blood DNA. The transcri pts code for a protein of 348 amino acids (aa), M(r) 38 962 (prior to any protein modification). The aa sequence suggests that in common wit h other sequenced Ops, canine rod Ops contains seven transmembrane dom ains, and residues believed essential for retinal pigment binding and for palmitate binding are conserved in the canine protein. Northern bl otting using the central part of the ops gene as probe suggested that mature transcripts of three different sizes (about 1900, 2600 and 5500 bases) were found in retina. Of these, the 2600-base transcript was t he most abundant. RACE cloning of the 3' end of ops showed that at lea st two of these size classes originate from differential transcript te rmination.