PH and Potential Transients of the bc1 Complex Co-Reconstituted in Proteo-Lipobeads with the Reaction Center from Rb. sphaeroides.

Abstract

His-tag technology is employed to bind membrane proteins, such as the bc1 complex and the reaction center (RC) from Rhodobacter sphaeroides, to spherical as well as planar surfaces in a strict orientation. Subsequently, the spherical and planar surfaces are subjected to in situ dialysis to form proteo-lipobeads (PLBs) and protein-tethered bilayer membranes, respectively. PLBs based on Ni-nitrileotriacetic acid-functionalized agarose beads that have diameters ranging from 50 to 150 μm are used to assess proton release and membrane potential parameters by confocal laser-scanning microscopy. The pH and potential transients are thus obtained from bc1 activated by the RC. To assess the turnover of bc1 excited by the RC in a similar setting, we used the planar surface of an attenuated total reflection crystal modified with a thin gold layer to carry out time-resolved surface-enhanced IR absorption spectroscopy triggered by flash lamp excitation. The experiments suggest that both proteins interact in a cyclic manner in both environments. The activity of the proteins seems to be preserved in the same manner as that in chromatophores or reconstituted in liposomes.