Structure and Assembly of the Photosynthetic Membrane of Rhodobacter Sphaeroides
Hoger, Jeffrey Harlen
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https://hdl.handle.net/2142/77645
Description
Title
Structure and Assembly of the Photosynthetic Membrane of Rhodobacter Sphaeroides
Author(s)
Hoger, Jeffrey Harlen
Issue Date
1986
Department of Study
Biology
Discipline
Biology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, General
Language
eng
Abstract
The structure of the photosynthetic reaction center of Rhodobacter sphaeroides was studied using chemical cross-linking reagents. Four intra-complex cross-linked polypeptide complexes were produced when purified reaction centers, reaction centers incorporated into liposomes, or intact chromatophore membranes were cross-linked. The complexes were composed of H-M, H-L, H-M-L, or L-M. The cross-linking of cytochrome c to soluble or membrane bound reaction centers was observed using any of the four cross-linking reagents. The products were a cytochrome c linked to either the M or L polypeptide. The results indicated L and M must be exposed from the membrane surface near a binding site for cytochrome c and all three subunits must be in close proximity.
Using a DNA-directed in vitro transcription-translation system derived from R sphaeroides, the synthesis of the three reaction subunits were verified by immunoprecipitation and Cleveland style digests. The properties of the in vitro synthesized polypeptides were examined by centrifugation. The polypeptides were not synthesized in a soluble form and associated in vitro with membranes. The cell-free system was modified to remove all endogenous membranes and reconstituted to synthesize the reaction center polypeptides. The modified in vitro system was optimized and the properties of the in vitro synthesized polypeptides examined.
Assembly of the photosynthetic membrane was also examined using synchronously growing cultures of R. sphaeroides. The chromatophore adenosine triphosphatase was measured throughout the cell cycle. The enzyme activity accumulated discontinuously. The response of the enzyme to an uncoupling reagent did not change during the cell cycle. When the adenosine triphosphatase was measured immunologically by Western blots, the enzyme mass accumulated continuously throughout the cell cycle.
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