J. Phys. IV France 125 (2005) 769-772
DOI: 10.1051/jp4:2005125177

Time-resolved enthalpy changes of Sensory Rhodopsin II and the transducer complex during photo-reaction

K. Inoue¹, J. Sasaki², M. Morisaki³, F. Tokunaga³ and M. Terazima<sup>1

1</sup>  Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
²  Center for Membrane Biology, Department of Biochemistry & Molecular Biology, University of Texas Health Science Center, 6431 Fannin, Houston, TX 77030-1503, USA
³  Department of Earth & Space Science, Graduate School of Science, Osaka University, Osaka 560-0055, Japan

Abstract
The dynamics of protein emthalpy change of Natronobacterium pharaonis sensory rhodopsin II (NpSRII) and of NpSRII fused to the transducer (NpHtrII) truncated at 159 amino acid sequence form the N-terminus (NpSRII-pHtrII) are investigated in solution phase at room temperature by the transient grating methods in real time. While kinetics of the photo-chemical reactions of both samples were similar to each other, significant difference was found in the molecular energy between NpSRII and NpSRII-NpHtrII samples. The enthalpy of the second intermediate (L) of NpSRII-NpHtrII is more stabilized compared with that of NpSRII. This stabilization indicates the influence of the transducer to the NpSRII structure in the early intermediate species by the complex formation.

© EDP Sciences 2005