Reaction dynamics of halorhodopsin studied by time-resolved diffusion.
Reaction dynamics of a chloride ion pump protein, halorhodopsin (HR), from Natronomonas pharaonis (N. pharaonis) (NpHR) was studied by the pulsed-laser-induced transient grating (TG) method. A detailed investigation of the TG signal revealed that there is a spectrally silent diffusion process besides the absorption-observable reaction dynamics. We interpreted these dynamics in terms of release, diffusion, and uptake of the Cl(-) ion. From a quantitative global analysis of the signals at various grating wavenumbers, it was concluded that the release of the Cl(-) ion is associated with the L2 --> (L2 (or N) <==> O) process, and uptake of Cl(-) occurs with the (L2 (or N) <==> O) -->NpHR' process. The diffusion coefficient of NpHR solubilized in a detergent did not change during the cyclic reaction. This result contrasts the behavior of many photosensor proteins and implies that the change in the H-bond network from intra- to intermolecular is not significant for the activity of this protein pump.
Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
Keiichi
K
Inoue
Megumi
M
Kubo
Makoto
M
Demura
Naoki
N
Kamo
Masahide
M
Terazima
D000465:Algorithms; D002712:Chlorides / Q000378:metabolism; D003198:Computer Simulation; D004058:Diffusion; D004926:Escherichia coli; D018014:Gene Transfer Techniques; D025602:Halorhodopsins / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008027:Light; D020125:Mutation, Missense; D019633:Natronobacterium; D013997:Time Factors
D002712:Chlorides; D025602:Halorhodopsins