title: Characterization of expressed pigmented core light harvesting complex (LH 1) in a reaction center deficient mutant of Blastochloris viridis.
abstract: The utility of photosynthetically defective mutants in the purple photosynthetic bacterium Blastochloris viridis (formerly Rhodopseudomonas viridis)was demonstrated with construction of a reaction-center deficient mutant, LH 1-H. This LH 1-H mutant has a photosynthetic apparatus in which most of the puf operon genes were deleted, resulting in an organism containing only the genes for the light harvesting polypeptides and the H subunit of the reaction center. This B. viridisstrain containing a truncation of the puf operon was characterized by gel electrophoresis, lipid-to-protein ratio analysis, optical spectroscopy, electron paramagnetic resonance and transmission electron microscopy. Optical and electron paramagnetic resonance spectroscopies revealed no photoactivity in this LH 1-H mutant consistent with the absence of intact reaction centers. Electron paramagnetic resonance evidence for assembled LH 1 complexes suggested that the interactions between light harvesting polypeptide complexes in membranes were largely unchanged despite the absence of their companion reaction center cores. The observed increase in the lipid-to-protein ratio was consistent with modified interactions between LH 1s, a view supported by transmission electron microscopy analysis of membrane fragments. The results show that B. viridis can serve as a practical system for investigating structure-function relationships in membranes and photosynthesis through the construction of photosynthetically defective mutants.
authors.affiliation: Department of Chemical Engineering, University of Notre Dame, 182 Fitzpatrick, Notre Dame, IN, 46556, USA.
authors.forename: Agnes E
authors.initials: AE
authors.lastname: Ostafin
authors.forename: Nina S
authors.initials: NS
authors.lastname: Ponomarenko
authors.forename: Julia A
authors.initials: JA
authors.lastname: Popova
authors.forename: Martin
authors.initials: M
authors.lastname: Jäger
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Bylina
authors.forename: James R
authors.initials: JR
authors.lastname: Norris