Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

Purpose. We have previously reported the discovery of a partial cDNA clone encoding a putative novel opsin (Soni and Foster, Invest. Opihalmol. Vis. Sei. 1996 Feb;37(3):#4265). A phylogcnetic analysis of this opsin shows that it diverges before the evolution of other vertebrate opsins. Thus, it has been named Ancient opsin (A-opsin). Our aim is to analyze the structural characteristics of full length A-opsin cDNA. Additionally, we wish to investigate the function of A-opsin pigment using functional expression with recombinant baculovirus. Methods. The remaining coding sequences of A-opsin were amplified from salmon ocular cDNA using 5′ and 3′ RACE PCR. A-opsin cDNA for expression was modified by addition of a carboxyl terminal 6X-histidine tag, enabling simple protein purification. Recombinant baculovirus was generated by homologous recombination with a transfer vector containing modified A-opsin cDNA. A-opsin protein was generated by infection of SF-9 cells with recombinant baculovirus. A-opsin was detected using a his-tag directed antibody. Results. Within opsin families, opsins from different species show amino acid identity of 65%-95%. Between families, they show identity of 40-50%. Full length A-opsin cDNA shows 32-42% identity with all other vertebrate opsin families. The new cDNA sequences reveal that A-opsin has several additional modifications. A-opsin has a short carboxyl tail with a singular serine residue and lacks a N terminal glycosylation site. Western blot analysis of infected SF-9 cells shows a his-tagged protein of 32 kDa indicating that we have expressed full length A-opsin protein. Conclusions. Based upon a partial clone, we had previously proposed that A-opsin forms a novel, and phylogenetically distinct, opsin class. Our analysis of full length A-opsin cDNA agrees with this hypothesis. We are currently investigating the spectral characteristics of A-opsin pigment in order to resolve the functional role of this novel opsin family.


Journal article


Investigative Ophthalmology and Visual Science

Publication Date