STUDIES TOWARDS THE CRYSTALLIZATION OF THE ROD VISUAL PIGMENT RHODOPSIN

The visual pigment rhodopsin is a member of the large family of G-protein coupled membrane receptors. To date, for none of these membrane proteins crystallization protocols have been reported. We have been able to establish a restricted range of conditions, which reproducibly yield crystals of bovine rhodopsin. Therefore, several parameters have been optimized (detergent, precipitant, additives, pH). So far, the crystals obtained usually are still too small ( < 50 mu m in any direction) or of unsufficient order to allow high-resolution diffraction analysis. Nevertheless, several novel concepts are introduced, which may be of a general use for this membrane protein family. Finally, several approaches are discussed to improve the average size, stability and/or order of the crystals.