Jul 3, 2013

Molecular dynamics simulations reveal highly permeable oxygen exit channels shared with water uptake channels in photosystem II

Biochimica Et Biophysica Acta
Serguei VassilievDoug Bruce


Photosystem II (PSII) catalyzes the oxidation of water in the conversion of light energy into chemical energy in photosynthesis. Water delivery and oxygen removal from the oxygen evolving complex (OEC), buried deep within PSII, are critical requirements to facilitate the reaction and minimize reactive oxygen damage. It has often been assumed that water and oxygen travel through separate channels within PSII, as demonstrated in cytochrome c oxidase. This study describes all-atom molecular dynamics simulations of PSII designed to investigate channels by fully characterizing the distribution and permeation of both water and oxygen. Interestingly, most channels found in PSII were permeable to both oxygen and water, however individual channels exhibited different energetic barriers for the two solutes. Several routes for oxygen diffusion within PSII with low energy permeation barriers were found, ensuring its fast removal from the OEC. In contrast, all routes for water showed significant energy barriers, corresponding to a much slower permeation rate for water through PSII. Two major factors were responsible for this selectivity: (1) hydrogen bonds between water and channel amino acids, and (2) steric restraints. Our results reveal ...Continue Reading

  • References28
  • Citations17


Mentioned in this Paper

Establishment and Maintenance of Localization
Molecular Dynamics
Biochemical Pathway
Cytochrome C Oxidase
Thylakoid Membrane
Entire Lumen of Body System
Amino Acids, I.V. solution additive
Energy Metabolism
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