BIOPHYSICAL THEORY AND MODELING |
Atomic Resolution Modeling of the Ferredoxin:[FeFe] Hydrogenase Complex from Chlamydomonas reinhardtii
Christopher H Chang 1*, Paul W King 1, Maria L Ghirardi 1 and Kwiseon Kim 1
1 National Renewable Energy Laboratory
* To whom correspondence should be addressed. E-mail: christopher_chang{at}nrel.gov.
Submitted on March 13, 2007
Revised on May 3, 2007
Accepted on 6 July 2007
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Abstract |
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The chloroplastic [FeFe] hydrogenases HydA1 and HydA2 in the green alga Chlamydomonas reinhardtii catalyze the final reaction in a remarkable metabolic pathway allowing this water-splitting photosynthetic organism to produce H2. [2Fe-2S] ferredoxin is a critical branch point in electron flow from photosystem I toward a variety of metabolic fates, including proton reduction by hydrogenases. To better understand the binding determinants involved in ferredoxin:hydrogenase interactions, we have modeled Chlamydomonas PetF1 and HydA2 based on amino acid sequence homology, and produced two promising electron-transfer model complexes by computational docking. To characterize these models, quantitative free energy calculations at atomic resolution were carried out, and detailed analysis of the interprotein interactions undertaken. The protein complex model we propose for ferredoxin:HydA2 interaction is energetically favored over the alternative candidate by 20 kcal/mol. This proposed model of the electron-transfer complex between PetF1 and HydA2 permits a more detailed view of the molecular events leading up to H2 evolution, and suggests potential mutagenic strategies to modulate electron flow to HydA2.
Key Words:
Chlamydomonas, binding, docking, electron transfer, ferredoxin, hydrogenase
