Structure and Function Relationships in Bioenergetic Systems: Photoreceptor Complexes and Mechanisms of Electron and Proton Transport

Supramolecular membrane complexes are responsible for achieving all major steps of energy conversion, whether they are involved in the capture of light, as in photosynthesis, or in the utilization of redox energy, as in mitochondrial electron transport. How these complexes are structured to carry out their task is the major interest of research in this laboratory. Photosynthetic bacteria are especially useful subjects for learning more abut these processes because these bacteria are able to both capture light energy by a supramolecular complex referred to as the photoreceptor complex (PRC) and to utilize redox energy to drive electron and proton transport in a manner nearly identical to that observed in mitochondria.

Our approach to understanding these supramolecular complexes is that of taking the complex apart and putting it back together again. The reconstitution of membrane complexes from their fundamental components allows the systematic probing of structure-function relationships. For example, our laboratory has developed reconstitution methodology for the study of the core light-harvesting complex (LH1) of photosynthetic bacteria and used it to define the specific interactions that hold the complex together and enable its function.

Of special interest in current work is to determine how LH1, the reaction center (RC) and the bc1 complex interact in the intact membrane. A protein component (called PufX protein) has recently been isolated by our laboratory and it seems to play a key role in facilitating the movement of reducing equivalents from the RC to the bc1 complex. The biochemical methodology is in place to evaluate the role of this protein and to characterize the interaction of these supramolecular complexes.

Parkes-Loach PS, Majeed AP, Law CJ and Loach PA(2004) Interactions stabilizing the structure of the core light-harvesting complex (LH1) of photosynthetic bacteria and its subunit (B820), Biochemistry , 43, 7003-7016.

Law CJ, Chen J, Parkes-Loach PS and Loach PA (2003)   Interaction of bacteriochlorophyll with the LH1 and PufX polypeptides of photosynthetic bacteria: use of chemically synthesized analogs and covalently attached fluorescent probes. Photosyn. Res. 75: 193-210.

Parkes-Loach PS,   Law CJ,   Recchia PA, Kehoe J, Nehrlich S, Chen J and Loach PA (2001)   Role of the core region of the pufx protein in inhibition of reconstitution of the core light-harvesting complexes of Rhodobacter sphaeroides and Rhodobacter capsulatus .   Biochemistry 40: 5593-5601.

View all publications by publications by Paul A. Loach listed in the National Library of Medicine (PubMed).