Organization of porphyrin derivatives using photosynthetic light-havesting polypeptide and its model polypeptide

点击翻译按钮获取中文摘要

The light-harvesting (LH) -a and -b polypeptides of photosynthetic bacteria organize a bachteriochlorophyll a (BChl a) complex according to cooperative interactions between the LH polypeptides and BChl a in a biologial membrane so that an efficient energy transfer between bacteriochlorophylls may occur in the LH complex. Work from several laboratories has demonstrated self-assemblies of porphyrins by using synthetic polypeptides to organize artificial hemoprotein models. However, there has been little study of molecular assembly of chlorophylls by using synthetic polypeptides to organize an artificial LH complex. Here, molecular assemblies of bacteriochloropyll a (BChl a) and its model compounds using light-harvesting (LH) polypeptide separately isolated from photosynthetic bacteria, Rhodospirllum rubrum (Rsp. rubrum) and its model synthetic polypeptides were examined in lipid bilayers as well as in n-Octyl-b-D-glucopyranoside (OG) micelle. Comparing the amino acid sequence in the N-and C-terminal segments of the LH polypeptide and its model peptides on the complex-formation with Zn-BChl a or BChl a reveals that the amino acid residues from M to F in the N-terminal segment of the LH polypeptide essentially account for the difference in the complex-formation between Zn-BChl a and BChl a. Interestingly, self-assembly of BChl a and its model compounds using the LH polypeptide and its model polypeptides in lipid bilayers was observed, analogous to an artificial LH 1-type complex. It is interesting to note that BChl a and its analogues complexes can be organized according to cooperative interactions between the LH polypeptide or its model polypeptides and bachteriochlorophyll derivatives.