2015
Volume 15, Number 2, pp. 55–62
Time course of purple membrane bending during the photocycle of bacteriorhodopsins
R. Tóth-Boconádi1 and L. Keszthelyi1, 2
1Institute of Biophysics, Biological Research Centre, Hungarian Academy of Sciences, P.O.B. 521, H-6701 Szeged, Hungary
2Institute for Particle and Nuclear Physics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, P.O.B. 49, H-1525 Budapest, Hungary
The bending under illumination of the purple membrane from Halobacterium salinarum (wild type and mutant D96N) was studied with the sensitive electro-optic method, in which the bending appears as a change in the orientation function due to the altered form of the membrane. It was found that the lifetime of appearance of bending coincides with the formation of the M intermediate of the bacteriorhodopsin photocycle while the decay is shorter (by about 20%) than the main component of its decay time. Moreover, a change in the opposite direction with substantial amplitude and a long lifetime was also recorded for the wild-type bacteriorhodopsin. Elastic forces in the membrane are proposed as the origin of these phenomena.
Keywords: electro-optic, M intermediate, membrane elasticity, orientation, quasi-continuous illumination