Structure-Function Relationship in Archaeal Retinal Proteins

Dieter Oesterhelt

Max-Planck-Institute for Biochemistry, Am Klopferspitz 18a, D-82152 Planegg-Martinsried, Germany


The family of retinal proteins from halophilic archaea is characterized by structural conservation and strong functional variation. The three basic functions of light-driven proton pumps, light-driven chloride pumps and photosensors with different absorption maxima are realized by variation of only two key residues, which are two aspartic acids in proton pumps, no carboxylate in chloride pumps and one aspartic acid in the sensors. All functions can be converted in the molecules either by specific physicochemical conditions or by point mutations. The key properties of these chromoproteins are colour changes of their active centre during the catalytic cycle, electric changes in the psec to msec range due to ion translocation and net ion concentration changes in vesicular systems. These three properties can be used for practical applications. The structural basis and the functional aspects of the retinal proteins essential for their biotechnology will be discussed in the lecture.