Synergetic mechanisms in energy and signal transduction: photo oscillating proton transport in bacteriorhodopsin.
Receptor proteins, linked with G-proteins and effector proteins, which act in signal information and energy transduction are key elements in biochemical systems that dissipate energy and rely on maintenance of order. Until now they have not yet been considered as elements for synergetic mechanisms. This paper describes the synergetic mechanisms of the archaebacterial signal and energy receptor bacteriorhodopsin (bR), for which, recently, light induced oscillations have been experimentally demonstrated. A synergetic mechanisms for proton pumping by this protein is presented. An important precondition is the ability of the molecule to significantly reduce its entropy (i.e. to increase its order through export of entropy) during the photo cycle. This should be paralleled by a systematic and organized change of pK values along the proton transducting "channel". The interaction of occupied and vacant protonation sites at such energized amino acid chains gives rise to feedback loops leading to an autocatalytic mechanism of proton transfer which, in combination with nonlinearities at the membrane interfaces and a time delay during the proton back flux, provides a simplified mechanism for oscillative light induced proton pumping. The expected relevance of autocatalytic and synergetic processes as inbuilt mechanisms for energy conversion and signal processing and the maintenance of order is discussed.
Tributsch
H
H
Hahn-Meitner-Institut, Dept. Solare Energetik, Berlin, Germany.
Pohlmann
L
L
D000596:Amino Acids / Q000378:metabolism; D001436:Bacteriorhodopsins / Q000378:metabolism*; D004735:Energy Transfer / Q000502:physiology*; D008027:Light; D008954:Models, Biological; D017494:Proton Pumps / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D013816:Thermodynamics
D000596:Amino Acids; D017494:Proton Pumps; D001436:Bacteriorhodopsins