ISSN:
1432-1017
Keywords:
Chloride pump
;
halorhodopsin
;
ion translocation
;
theoretical model
;
cis-trans isomerization
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Physics
Notes:
Abstract The chromophore in halorhodopsin (HR) which acts as a light-driven chloride pump in halobacteria shares many properties with its counterpart in bacteriorhodopsin (BR): (i) a similar retinal protein interaction, (ii) trans to cis isomerization and (iii) similar intermediates of its photocycle. One major difference between the two chromoproteins is that the HR chromophore does not become deprotonated during its photocycle. A mechanism for the photocycle of HR is presented, which, in close analogy to an earlier proposed mechanism for BR, involves the sequence of all-trans → 13-cis, 14s-cis → 13-cis → all-trans isomerizations of the chromophore, a Schiff base of retinal. In contrast to the situation in BR the 13-cis, 14s-cis→13-cis isomerization is induced not by deprotonation of the retinal Schiff base chromophore but rather by the movement of an anion (Cl-) towards the protonated nitrogen of the Schiff's base. The suggested mechanism involves the Schiff base directly in the chloride translocation in halorhodopsin.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00263069
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