Interaction between Cytochrome c2 and Reaction Centers from Purple Bacteria

Abstract

The kinetics of electron transfer of cytochrome c2 from Rhodobacter sphaeroides, Rhodobacter capsulatus, and Rhodospirillum centenum to reaction centers from Rb. sphaeroides and Rb. capsulatus have been measured. Observed in the kinetics of decay of the oxidized donor are a rapid first-order rate and one or more slower rates that are due to diffusion-limited complex formation. For reaction centers from Rb. sphaeroides, the fast component had time constants of 1.0 and 0.5 microsecond for cytochrome c2 from Rb. sphaeroides and Rb. capsulatus, respectively, but only a slow component was observed for cytochrome c2 from Rs. centenum. For reaction centers from Rb. capsulatus, the kinetics from all three cytochromes had a fast component with time constants of 1.0, 0.7, and 1.9 microseconds for cytochrome c2 from Rb. sphaeroides, Rb. capsulatus, and Rs. centenum, respectively, although the dissociation constant for cytochrome c2 from Rs. centenum was approximately 20 times larger than that of the other cytochromes. The observation of the fast component for cytochrome c2 from Rs. centenum in reaction centers from Rb. capsulatus but not Rb. sphaeroides demonstrates that the binding interactions for the two reaction centers differ, and the involvement of amino acid residues in the binding is discussed. The kinetics of electron transfer from cytochrome c2 to reaction centers of Rb. sphaeroides from wild type and three mutant strains that have altered carboxyl-terminal regions of the M subunit of the reaction center have also been measured. For cytochrome c2 from Rb. sphaeroides, the kinetics are very similar between the mutants and wild type.(ABSTRACT TRUNCATED AT 250 WORDS)

Nonredundant Roles for Cytochrome c 2 and Two High-Potential Iron-Sulfur Proteins in the Photoferrotroph Rhodopseudomonas palustris TIE-1

“…Cytochrome c 2 has been extensively studied in several purple bacterial species (28,30,31), and the protein found in TIE-1 appears to be typical of this family. Its reduction potential (ϩ350 mV) is typical of cytochromes c 2 , and our experiments with purified protein and membrane fragments show that the electron transfer rate from cytochrome c 2 to the reaction center is within the range found in other purple bacteria (8,32).…”

A High‐Potential Soluble Cytochrome C ‐551 from the Purple Phototrophic Bacterium Chromatium vinosum is Homologous to Cytochrome C8 from Denitrifying Pseudomonads

“…5 ) but no one has demonstrated its role in photosynthesis. The only type of cytochrome that has been clearly demonstrated to be the electron-donor partner of the photoreaction cen-69.5 ter is the cytochrome c, from the non-sulfur bacteria Rhodobacter sphaeroides and Rhodobacter capsulatus (Donohue et al, 1988;Jenney and Daldal, 1993;Wang et al, 1994;Meyer and Donohue, 1995). C. vinosum, which in contrast with the latter bacteria has a tetrahaem cytochrome associated with its reaction center, may consequently have a cytochrome donor different from a c,-like protein.…”

The high potential iron‐sulfur protein (HiPIP) from Rhodoferax fermentans is competent in photosynthetic electron transfer

“…This indicates that the quinol oxidase, which accepts electrons from the RC-generated quinols, is not saturated under our experimental conditions. These findings suggest that electron transfer would occur between HiPIP and RC, possibly via the formation of a complex, as previously observed in analogous photosynthetic systems involving soluble c-type cytochromes and RCs [11,[20][21][22]. To test this hypothesis, we analyzed, using kinetic spectrophotometry, the absorbance changes related to RC-induced cytochrome oxidation.…”