Aikaterini Rousaki

Dr Aikaterini Rousaki

Research:

The family of the seven-helix rhodopsin proteins is a family of membrane proteins that contain retinal as a chromophore and sensory rhodopsin II (SRII) is a member of this class. Various members of the family that function as proton pumps and as photoreceptors have been studied. Examples of such proteins are proteorhodopsin[1], bacteriorhodopsin [2]and sensory SRII (also known as phoborhodopsin [3]). All rhodopsins are light-activatable proteins. In their photocycle, short-lived metastable intermediate states (K, L, M, N, O, P) are populated. The lifetime of these states varies among the rhodopsin proteins and the conditions of their study. The time constants of this cycle are controversial and ambiguities do occur in the bibliography [4, 5]. My research is focused on trapping those intermediates using LASER excitation and to study structurally those intermediates. A novel technique that combines LASER excitation of the sample and NMR recording of the metastable long lived intermediates is being used and NMR spectroscopy is investigating states of the SRII photocycle that have never been studied before. 1 O. Beja, E. N. Spudich, J. L. Spudich, M. Leclerc, and E. F. DeLong, Nature 411 (6839), 786 (2001). 2 H. Luecke and J. K. Lanyi, Membrane Proteins 63, 111 (2003). 3 W. D. Hoff, K. H. Jung, and J. L. Spudich, Annual Review of Biophysics and Biomolecular Structure 26, 223 (1997); J. P. Klare, E. Bordignon, M. Engelhard, and H. J. Steinhoff, Photochemical & Photobiological Sciences 3 (6), 543 (2004). 4 T. Friedrich, S. Geibel, R. Kalmbach, I. Chizhov, K. Ataka, J. Heberle, M. Engelhard, and E. Bamberg, Journal of Molecular Biology 321 (5), 821 (2002). 5 G. Varo, L. S. Brown, M. Lakatos, and J. K. Lanyi, Biophysical Journal 84 (2), 1202 (2003).