J. Phys. IV France
Volume 125, June 2005
Page(s) 769 - 772

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. Terazima1

1  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

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-$\delta$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-$\delta$NpHtrII samples. The enthalpy of the second intermediate (L) of NpSRII-$\delta$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