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. 1958 Nov 20;42(2):259–280. doi: 10.1085/jgp.42.2.259

THE THERMAL STABILITY OF RHODOPSIN AND OPSIN

Ruth Hubbard 1
PMCID: PMC2194909  PMID: 13587911

Abstract

Rhodopsin, the red photosensitive pigment of rod vision, is composed of a specific cis isomer of retinene, neo-b (11-cis), joined as chromophore to a colorless protein, opsin. We have investigated the thermal denaturation of cattle rhodopsin and opsin in aqueous digitonin solution, and in isolated rod outer limbs. Both rhodopsin and opsin are more stable in rods than in solution. In solution as well as in rods, moreover, rhodopsin is considerably more stable than opsin. The chromophore therefore protects opsin against denaturation. This is true whether rhodopsin is extracted from dark-adapted retinas, or synthesized in vitro from neo-b retinene and opsin. Excess neo-b retinene does not protect rhodopsin against denaturation. The protection involves the specific relationship between the chromophore and opsin. Similar, though somewhat less, protection is afforded opsin by the stereoisomeric iso-a (9-cis) chromophore in isorhodopsin. The Arrhenius activation energies (Ea) and entropies of activation (ΔS‡) are much greater for thermal denaturation of rhodopsin and isorhodopsin than of opsin. Furthermore, these values differ considerably for rhodopsins from different species —frog, squid, cattle—presumably due to species differences in the opsins. Heat or light bleaches rhodopsin by different mechanisms, yielding different products. Light stereoisomerizes the retinene chromophore; heat denatures the opsin. Photochemical bleaching therefore yields all-trans retinene and native opsin; thermal bleaching, neo-b retinene and denatured opsin.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. BARLOW H. B. Purkinje shift and retinal noise. Nature. 1957 Feb 2;179(4553):255–256. doi: 10.1038/179255b0. [DOI] [PubMed] [Google Scholar]
  2. DENTON E. J., PIRENNE M. H. The absolute sensitivity and functional stability of the human eye. J Physiol. 1954 Mar 29;123(3):417–442. doi: 10.1113/jphysiol.1954.sp005062. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. HUBBARD R. Bleaching of rhodopsin by light and by heat. Nature. 1958 Apr 19;181(4616):1126–1126. doi: 10.1038/1811126a0. [DOI] [PubMed] [Google Scholar]
  4. HUBBARD R. Retinene isomerase. J Gen Physiol. 1956 Jul 20;39(6):935–962. doi: 10.1085/jgp.39.6.935. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. HUBBARD R., ST GEORGE R. C. The rhodopsin system of the squid. J Gen Physiol. 1958 Jan 20;41(3):501–528. doi: 10.1085/jgp.41.3.501. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. HUBBARD R., WALD G. Cis-trans isomers of vitamin A and retinene in the rhodopsin system. J Gen Physiol. 1952 Nov;36(2):269–315. doi: 10.1085/jgp.36.2.269. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Hubbard R., Kropf A. THE ACTION OF LIGHT ON RHODOPSIN. Proc Natl Acad Sci U S A. 1958 Feb;44(2):130–139. doi: 10.1073/pnas.44.2.130. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Lythgoe R. J., Quilliam J. P. The thermal decomposition of visual purple. J Physiol. 1938 Jun 14;93(1):24–38. doi: 10.1113/jphysiol.1938.sp003622. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Mirsky A. E. The Visual Cycle and Protein Denaturation. Proc Natl Acad Sci U S A. 1936 Feb;22(2):147–149. doi: 10.1073/pnas.22.2.147. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. RADDING C. M., WALD G. The stability of rhodopsin and opsin; effects of pH and aging. J Gen Physiol. 1956 Jul 20;39(6):923–933. doi: 10.1085/jgp.39.6.923. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. WALD G., BROWN P. K. Human rhodopsin. Science. 1958 Jan 31;127(3292):222–226. doi: 10.1126/science.127.3292.222. [DOI] [PubMed] [Google Scholar]
  12. WALD G., BROWN P. K. The role of sulfhydryl groups in the bleaching and synthesis of rhodopsin. J Gen Physiol. 1952 May;35(5):797–821. doi: 10.1085/jgp.35.5.797. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. WALD G., DURELL J., ST GEORGE C. C. The light reaction in the bleaching of rhodopsin. Science. 1950 Feb 17;111(2877):179–181. doi: 10.1126/science.111.2877.179. [DOI] [PubMed] [Google Scholar]
  14. WALD G., HUBBARD R. The reduction of retinene1 to vitamina A1 in vitro. J Gen Physiol. 1949 Jan;32(3):367–389. doi: 10.1085/jgp.32.3.367. [DOI] [PMC free article] [PubMed] [Google Scholar]

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