Open AccessRole of the H Protein in Assembly of the Photochemical Reaction Center and Intracytoplasmic Membrane in Rhodospirillum rubrum
Author(s) -
Yongjian S. Cheng,
Christine A. Brantner,
A. I. Tsapin,
Mary Lynne Perille Collins
Publication year - 2000
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.182.5.1200-1207.2000
Subject(s) - rhodospirillum rubrum , biology , photosynthetic reaction centre , rhodospirillales , operon , mutant , bacteriochlorophyll , rhodospirillaceae , purple bacteria , biochemistry , gene , photosynthesis , enzyme
Rhodospirillum rubrum is a model for the study of membrane formation. Under conditions of oxygen limitation, this facultatively phototrophic bacterium forms an intracytoplasmic membrane that houses the photochemical apparatus. This apparatus consists of two pigment-protein complexes, the light-harvesting antenna (LH) and photochemical reaction center (RC). The proteins of the photochemical components are encoded by thepuf operon (LHα, LHβ, RC-L, and RC-M) and bypuhA (RC-H).R. rubrum puf interposon mutants do not form intracytoplasmic membranes and are phototrophically incompetent. Thepuh region was cloned, and DNA sequence determination identified open reading framesbchL andbchM and part ofbchH ;bchHLM encode enzymes of bacteriochlorophyll biosynthesis. ApuhA /G115 interposon mutant was constructed and found to be incapable of phototrophic growth and impaired in intracytoplasmic membrane formation. Comparison of properties of the wild-type and the mutated and complemented strains suggests a model for membrane protein assembly. This model proposes that RC-H is required as a foundation protein for assembly of the RC and highly developed intracytoplasmic membrane. In complemented strains, expression ofpuh occurred under semiaerobic conditions, thus providing the basis for the development of an expression vector. ThepuhA gene alone was sufficient to restore phototrophic growth provided that recombination occurred.