Abstract
The recent crystallographic structure at 3.0 Å resolution of PSII from Thermosynechococcus elongatus has revealed a cavity in the protein which connects the membrane phase to the binding pocket of the secondary plastoquinone Q B. The cavity may serve as a quinone diffusion pathway. By fluorescence methods, electron transfer at the donor and acceptor sides was investigated in the same membrane-free PSII core particle preparation from T. elongatus prior to and after crystallization; PSII membrane fragments from spinach were studied as a reference. The data suggest selective enrichment of those PSII centers in the crystal that are intact with respect to O 2 evolution at the manganese–calcium complex of water oxidation and with respect to the integrity of the quinone binding site. One and more functional quinone molecules (per PSII monomer) besides of Q A and Q B were found in the crystallized PSII. We propose that the extra quinones are located in the Q B cavity and serve as a PSII intrinsic pool of electron acceptors.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
More From: Biochimica et Biophysica Acta (BBA) - Bioenergetics
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.