Characterization of the ground state dynamics of proteorhodopsin by NMR and optical spectroscopies
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Characterization of the ground state dynamics of proteorhodopsin by NMR and optical spectroscopies Jochen Stehle • Frank Scholz • Frank Lo¨hr • Sina Reckel • Christian Roos • Michaela Blum • Markus Braun • Clemens Glaubitz Volker Do¨tsch • Josef Wachtveitl • Harald Schwalbe
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Received: 28 August 2012 / Accepted: 2 November 2012 / Published online: 17 November 2012 Ó Springer Science+Business Media Dordrecht 2012
Abstract We characterized the dynamics of proteorhodopsin (PR), solubilized in diC7PC, a detergent micelle, by liquid-state NMR spectroscopy at T = 323 K. Insights into the dynamics of PR at different time scales could be obtained and dynamic hot spots could be identified at distinct, functionally relevant regions of the protein, including the BC loop, the EF loop, the N-terminal part of helix F and the C-terminal part of helix G. We further characterize the dependence of the photocycle on different detergents (nDodecyl b-D-maltoside DDM; 1,2-diheptanoyl-sn-glycero3-phosphocholine diC7PC) by ultrafast time-resolved UV/ VIS spectroscopy. While the photocycle intermediates of PR in diC7PC and DDM exhibit highly similar spectral characteristics, significant changes in the population of these intermediates are observed. In-situ NMR experiments have been applied to characterize structural changes during the Electronic supplementary material The online version of this article (doi:10.1007/s10858-012-9684-8) contains supplementary material, which is available to authorized users. J. Stehle H. Schwalbe (&) Institute for Organic Chemistry and Chemical Biology, Goethe University Frankfurt, 60438 Frankfurt, Germany e-mail: [email protected] J. Stehle F. Lo¨hr S. Reckel C. Roos M. Blum C. Glaubitz V. Do¨tsch H. Schwalbe Center of Biomolecular Magnetic Resonance, Goethe University Frankfurt, 60438 Frankfurt, Germany F. Scholz M. Braun J. Wachtveitl Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, 60438 Frankfurt, Germany F. Lo¨hr S. Reckel C. Roos M. Blum C. Glaubitz V. Do¨tsch Institute of Biophysical Chemistry, Goethe University Frankfurt, 60438 Frankfurt, Germany
photocycle. Light-induced chemical shift changes detected during the photocycle in diC7PC are very small, in line with the changes in the population of intermediates in the photocycle of proteorhodopsin in diC7PC, where the late O-intermediate populated in DDM is missing and the population is shifted towards an equilibrium of intermediates states (M, N, O) without accumulation of a single populated intermediate. Keywords Proteorhodopsin Photocycle Membrane protein dynamics NMR spectroscopy Abbreviations PR Proteorhodopsin BR Bacteriorhodopsin FT Fourier transform IR Infrared diC7PC 1,2-diheptanoyl-sn-glycero-3-phosphocholine DDM n-Dodecyl b-D-maltoside NMR Nuclear magnetic resonance MES 2-(N-morpholino)ethanesulfonic acid SRII Sensory rhodopsin II UV Ultra violet
Introduction Light is one of the most interesting environmental factors; it plays a prominent role in informa
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