title: Assembly of photosystem I. II. Rubredoxin is required for the in vivo assembly of F(X) in Synechococcus sp. PCC 7002 as shown by optical and EPR spectroscopy.
abstract: The rubA gene was insertionally inactivated in Synechococcus sp. PCC 7002, and the properties of photosystem I complexes were characterized spectroscopically. X-band EPR spectroscopy at low temperature shows that the three terminal iron-sulfur clusters, F(X), F(A), and F(B), are missing in whole cells, thylakoids, and photosystem (PS) I complexes of the rubA mutant. The flash-induced decay kinetics of both P700(+) in the visible and A(1)- in the near-UV show that charge recombination occurs between P700(+) and A(1)- in both thylakoids and PS I complexes. The spin-polarized EPR signal at room temperature from PS I complexes also indicates that forward electron transfer does not occur beyond A(1). In agreement, the spin-polarized X-band EPR spectrum of P700(+) A(1)- at low temperature shows that an electron cycle between A(1)- and P700(+) occurs in a much larger fraction of PS I complexes than in the wild-type, wherein a relatively large fraction of the electrons promoted are irreversibly transferred to [F(A)/F(B)]. The electron spin polarization pattern shows that the orientation of phylloquinone in the PS I complexes is identical to that of the wild type, and out-of-phase, spin-echo modulation spectroscopy shows the same P700(+) to A(1)- center-to-center distance in photosystem I complexes of wild type and the rubA mutant. In contrast to the loss of F(X), F(B), and F(A), the Rieske iron-sulfur protein and the non-heme iron in photosystem II are intact. It is proposed that rubredoxin is specifically required for the assembly of the F(X) iron-sulfur cluster but that F(X) is not required for the biosynthesis of trimeric P700-A(1) cores. Since the PsaC protein requires the presence of F(X) for binding, the absence of F(A) and F(B) may be an indirect result of the absence of F(X).
authors.affiliation: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: Gaozhong
authors.initials: G
authors.lastname: Shen
authors.forename: Mikhail L
authors.initials: ML
authors.lastname: Antonkine
authors.forename: Art
authors.initials: A
authors.lastname: van der Est
authors.forename: Ilya R
authors.initials: IR
authors.lastname: Vassiliev
authors.forename: Klaus
authors.initials: K
authors.lastname: Brettel
authors.forename: Robert
authors.initials: R
authors.lastname: Bittl
authors.forename: Stephan G
authors.initials: SG
authors.lastname: Zech
authors.forename: Jindong
authors.initials: J
authors.lastname: Zhao
authors.forename: Dietmar
authors.initials: D
authors.lastname: Stehlik
authors.forename: Donald A
authors.initials: DA
authors.lastname: Bryant
authors.forename: John H
authors.initials: JH
authors.lastname: Golbeck
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D000458:Cyanobacteria / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D013696:Temperature
chemical_list: D001426:Bacterial Proteins