Organization of Photosynthetic Antenna Complex in Lipid Bilayers
Bacterial photosynthetic antenna complexes are composed of α-helical hydrophobic polypeptides and pigments (e.g., bacteriochlorophyll a). We report here self-assembling properties of an engineered hydrophobic polypeptide with zinc-substituted bacteriochlorophyll a ([Zn]-BChl a) in various lipid bilayer to investigate the effect of lipid species on the self-assembling properties. When the polypeptide and [Zn]-BChl a were mixed in surfactant solution (n-octyl β-D-glucopyranoside: OG) at 25°C, the absorption band [Zn]-BChl a was red-shifted from 770 to 812 nm, that is assignable to quasi-dimeric “subunit-type” complex. By subsequent dilution and cooling of the solution, the absorption band further red-shifted to 836 nm indicative for progressed assembly, ‘LH1-type’ complex. When the subunit-type complex was assembled in lipid bilayer, e.g., phosphatidylcholines (PC’s) and phosphatidylglycerol (PG’s), the assembling property to form LH1-type complex prominently depended on the character of their fatty acid chains in the phospholipids. The subunit complex remained in the fluidic bilayers, but further assembled to form LH1-type complex in solid-like phospholipid bilayers, suggesting that intermolecular force of phospholipid governs the assembling of the polypeptide/[Zn]-BChl a complex.
Masayuki Nogami, Riguang Jin, Toshihiro Kasuga and Wantai Yang
T. Dewa et al., "Organization of Photosynthetic Antenna Complex in Lipid Bilayers", Advanced Materials Research, Vols. 11-12, pp. 623-626, 2006