Transient light-induced conformational changes in rhodopsin.

Arguments are presented which support the possibility that the unfolding of the rhodopsin molecule during photolysis up to the stage of metarhodopsin II is followed by a spontaneous refolding of the protein, once the isomerized retinaldehyde has left its original binding site. Such a transient conformational change might imply a very similar conformation for rhodopsin and opsin, apart from the presence of the chromophore.