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Role of the N- and C-terminal regions of the PufX protein in the structural organization of the photosynthetic core complex of Rhodobacter sphaeroides

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http://pubman.mpdl.mpg.de/cone/persons/resource/persons77968

Francia,  F.
Oesterhelt, Dieter / Membrane Biochemistry, Max Planck Institute of Biochemistry, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons78856

Wang,  J.
Oesterhelt, Dieter / Membrane Biochemistry, Max Planck Institute of Biochemistry, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons78937

Zischka,  H.
Oesterhelt, Dieter / Membrane Biochemistry, Max Planck Institute of Biochemistry, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons78468

Oesterhelt,  D.
Oesterhelt, Dieter / Membrane Biochemistry, Max Planck Institute of Biochemistry, Max Planck Society;

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Citation

Francia, F., Wang, J., Zischka, H., Venturoli, G., & Oesterhelt, D. (2002). Role of the N- and C-terminal regions of the PufX protein in the structural organization of the photosynthetic core complex of Rhodobacter sphaeroides. European Journal of Biochemistry, 269(7), 1877-1885.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0010-6F7C-1
Abstract
The core complex of Rhodobacter sphaeroides is formed by the association of the light-harvesting antenna 1 (LH1) and the reaction center (RC). The PufX protein is essential for photosynthetic growth; it is located within the core in a 1 : 1 stoichiometry with the RC. PufX is required for a fast ubiquinol exchange between the Q(B) site of the RC and the Qo site of the cytochrome bc(1) complex. In vivo the LH1-PufX-RC complex is assembled in a dimeric form, where PufX is involved as a structural organizer. We have modified the PufX protein at the N and the C-terminus with progressive deletions. The nine mutants obtained have been characterized for their ability for photosynthetic growth, the insertion of PufX in the core LH1-RC complex, the stability of the dimers and the kinetics of flash- induced reduction of cytochrome b(561) of the cytochrome bc(1) complex. Deletion of 18 residues at the N-terminus destabilizes the dimer in vitro without preventing photosynthetic growth. The dimer (or a stable dimer) does not seem to be a necessary requisite for the photosynthetic phenotype. Partial C-terminal deletions impede the insertion of PufX, while the complete absence of the C-terminus leads to the insertion of a PufX protein composed of only its first 53 residues and does not affect the photosynthetic growth of the bacterium. Overall, the results point to a complex role of the N and C domains in the structural organization of the core complex; the N-terminus is suggested to be responsible mainly for dimerization, while the C-terminus is thought to be involved mainly in PufX assembly.