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Robert A. Niederman
Professor
Rutgers University
Dept. of Molecular Biology and Biochemistry
Nelson Hall. A317
Busch Campus. Rutgers University
Piscataway. NJ 08854
(732) 445-3985
FAX - 4213
rniederm@rci.rutgers.edu |
Structure, function, and assembly of photosynthetic membranes
A variety of integrated biochemical. biophysical and molecular genetica approaches are used to investigate the structural organization and assembly of photosynthetic membranes in purple nonsulfur proteobacteria. an experimentally accessible prokaryotic model system. These membrane structures contain integral light-harvesting complexes which transfer excitations to photochemical reaction center. This initiates cyclic electron transfer through a mitochondrial-type cytochrome bc1 complex. resulting in re-reduction of the photooxidized reaction center and conservation of the light energy as an electrochemical proton gradient coupled to the synthesis of ATP.
The role which noncatalytic subunits play in electron transport complexes is being examined in the Rhodobacter sphaeroides cytochrome bc1 complex. which contains a unique polypeptide (subunit IV) lacking a prosthetic group. We have recently elucidated the membrane topology of this integral membrane protein and have constructed strains from which its structural gene has been deleted. This is serving as a basis for determining whether subunit IV is functionally essential. or has important structural and assembly roles. A second area of investigation involves elucidation of the structural basis for rapid and efficient excitation energy transfer by integral membrane light-harvesting complexes. The questions currently under investigation include: the nature of functionally crucial bacteriochlorophyll-protein and apoprotein associations in the peripheral light-harvesting proteins; the role of spectral heterogeneity in facilitating directed energy transfer from core light-harvesting complexes to the reaction center; determining how singlet excitation energy transfer from carotenoids to bacterioclorophyll competes with deexcitation processes; and the role which an open reading frame (pufX). located immediately downstream from genes encoding core light-harvesting and reaction center polypeptides. plays in the organization of photosynthetic units.
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