Cloning of the cDNA for a novel photoreceptor protein

Tomomi Higashide, Akira Murakami, Margaret J. McLaren, George Inana

Research output: Contribution to journalArticlepeer-review

50 Scopus citations


A subtractive cDNA cloning strategy was used to isolate a 1381-base pair human retina-specific cDNA, human retinal gene 4 (HRG4), which hybridized to a 1.4-kilobase message in the retina and encoded a 240-amino acid acidic protein with a calculated molecular mass of 26,964 Da. The proximal 1/4 of the conceptual protein sequence was rich in glycine (18%) and proline (20%), had a predicted secondary structure of turns, and showed a loose similarity (19-24%) to various α-collagen sequences, while the distal 3/4 consisted of a mixture of α-helices, β-sheets, and turns. Genomic Southern analysis with HRG4 showed cross-hybridizing sequences in six different species, and HRG4 was 92% homologous with a 1204-base pair rat eDNA (rat retinal gene 4; RRG4) at the protein level. The region of 100% identity between the two sequences corresponded to the distal 3/4 of the protein sequence consisting of mixed secondary structures, suggesting a functionally important domain. In vitro transcription and translation corroborated the open reading frames corresponding to HRG4 and RRG4 in the cDNAs. Expression of HRG4 in the retina was localized to the photoreceptors by in situ hybridization. Developmentally, RRG4 began to be highly expressed around postnatal day 5 in the rat outer retina when the photoreceptors begin to differentiate and rapidly increased in expression to reach the mature adult level by postnatal day 23. No diurnal fluctuation in expression of RRG4 was seen.

Original languageEnglish (US)
Pages (from-to)1797-1804
Number of pages8
JournalJournal of Biological Chemistry
Issue number3
StatePublished - Jan 19 1996

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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