Section 7
Chapter 6,283

Regeneration of rhod opsin and bacterio rhod opsin role of retinal analogs as inhibitors

Towner, P.; Gaertner, W.; Walckhoff, B.; Oesterhelt, D.; Hopf, H.

European Journal of Biochemistry 117(2): 353-360


ISSN/ISBN: 0014-2956
Accession: 006282741

The rate of regeneration of rhodopsin (isolated from retina rod outer segments) from 11-cis-retinal and opsin and bacteriorhodopsin (isolated from Halobacterium halobium) from all-trans-retinal and bacterioopsin in the presence or absence of compounds whose structures partially resemble retinal were measured. Some compounds severely slowed down the regeneration process, but did not influence the extent of regeneration. In the case of compounds with a carbonyl functional group they were not joined to the active site of the apo-protein via a Schiff's base linkage since after treatment with NaBH4 an active apo-protein remained. The most effective inhibitors of rhodopsin regeneration were molecules whose structure could be superimposed on 9-cis or 11-cis retinal up to C atom 11. These C13 and C15 molecules were not distinguished between aldehyde, ketone or alcohol functional groups. The regeneration of bacteriorhodopsin was not inhibited by retinal analogs with short side chains. The most effective inhibitors were the all-trans C17-aldehyde (.beta.-ionylideneacetaldehyde) or C18-ketone (.beta.-ionylidenepent-3-ene-2-one) which, compared to retinal, lack 2 or 3 C atoms from the end of the polyene chain. The inhibition was very dependent upon the presence of the all-trans isomer and required aldehyde or ketone as functional group; nitriles and alcohols were less effective. Similarly to retinol, the all-trans C17 and C18 alcohols underwent a bathochromic shift and showed fine-structured spectra when mixed with bacterioopsin.

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