Structural changes in the lumirhodopsin-to-metarhodopsin I conversion of air-dried bovine rhodopsin.
Structural changes during the photochemical reactions of unhydrated air-dried films of bovine rhodopsin in rod outer segments were examined by visible and Fourier transform infrared (FTIR) spectroscopy at 200, 240, and 280 K. These films exhibited conversion from a lumirhodopsin state to a metarhodopsin I state with a time constant of 13.5 min at 280 K, but did not form metarhodopsin II at all, as observed earlier for digitonin-extracted rhodopsin in dry gelatin films [Wald, Durell, and St. George (1950) Science 111, 179-181]. Lumirhodopsin which was stable in the dry film was very similar to normal lumirhodopsin. The metarhodopsin I-like state retained properties characteristic of lumirhodopsin in regard to a twisted structure between the C14-H and the Schiff base of the chromophore, and perturbation around Glu122, although the C-C stretch frequencies of the chromophore were identical with those of metarhodopsin I. Thus, under dry conditions some of the structural changes that lead to metarhodopsin I are partially inhibited. These defects could result in stable lumirhodopsin and the failure to form metarhodopsin II, which is in equilibrium with metarhodopsin I.
Department of Biophysics, Faculty of Science, Kyoto University, Japan.
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S
Nishimura
J
J
Sasaki
H
H
Kandori
J
J
Lugtenburg
A
A
Maeda
D000818:Animals; D002417:Cattle; D066298:In Vitro Techniques; D015394:Molecular Structure; D010777:Photochemistry; D012243:Rhodopsin / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000528:radiation effects*; D012374:Rod Cell Outer Segment / Q000737:chemistry; D012545:Schiff Bases / Q000737:chemistry; D013053:Spectrophotometry; D017550:Spectroscopy, Fourier Transform Infrared
D012545:Schiff Bases; C018586:lumirhodopsin; C013110:metarhodopsins; D012243:Rhodopsin