Abstract:
:Both the solution and the oriented film absorption and circular dichroic spectra of the bacteriorhodopsin (bR(568)) and M(412) intermediate of the purple membrane photocycle were compared over the wavelength region 800-183 nm to assess structural changes during this photocycle. The main findings are (a) loss of the excitonic interaction among the chromophoric retinal transitions indicating disordering of the retinal orientations in the membrane and distortions of the membrane hexagonal crystal lattice, (b) structural change of the chromophoric retinal, (c) changes in the key interactions between the retinal and specific groups in the local environment of the apoprotein, (d) significant changes of the tertiary structure of the bR with negligible secondary structure involvement, and (e) a net tilting of the rodlike segments of the bR polypeptides away from the membrane normal. These findings are in accord with large scale global structural changes of the membrane during the photocycle and with structural metastability of the bR molecules. An important implication of these changes is the possibility of transmembrane retinal-regulated pulsating channels during the photocycle. The significance of this possibility in respect to models for the proton translocation function of this membrane is discussed.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Draheim JE,Cassim JYdoi
10.1016/S0006-3495(85)83943-6subject
Has Abstractpub_date
1985-04-01 00:00:00pages
497-507issue
4eissn
0006-3495issn
1542-0086pii
S0006-3495(85)83943-6journal_volume
47pub_type
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