title: Structure and Function of Photosystem I-[FeFe] Hydrogenase Protein Fusions: An All-Atom Molecular Dynamics Study.
abstract: All-atom molecular dynamics (MD) simulation was used to study the solution dynamics and protein-protein interactions of protein fusions of photosystem I (PSI) from Thermosynechococcus elongatus and an [FeFe]-hydrogenase (FeFe H2ase) from Clostridium pasteurianum, a unique complex capable of photocatalytic hydrogen production. This study involved fusions of these two proteins via dithiol linkers of different length including decanedithiol, octanedithiol, and hexanedithiol, for which experimental data had previously been obtained. Evaluation of root-mean-squared deviations (RMSDs) relative to the respective crystal structures of PSI and the FeFe H2ase shows that these fusion complexes approach stable equilibrium conformations during the MD simulations. Investigating protein mobility via root-mean-squared fluctuations (RMSFs) reveals that tethering via the shortest hexanedithiol linker results in increased atomic fluctuations of both PSI and the hydrogenase in these fusion complexes. Evaluation of the inter- and intraprotein electron transfer distances in these fusion complexes indicates that the structural changes in the FeFe H2ase arising from ligation to PSI via the shortest hexanedithiol linker may hinder electron transport in the hydrogenase, thus providing a molecular level explanation for the observation that the medium-length octanedithiol linker gives the highest hydrogen production rate.
authors.affiliation: College of Engineering and Computer Science, University of Tennessee , Chattanooga, Tennessee 37403, United States.
authors.forename: Bradley J
authors.initials: BJ
authors.lastname: Harris
authors.affiliation: Center for Molecular Biophysics, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Cheng
authors.forename: Paul
authors.initials: P
authors.lastname: Frymier
mesh_terms: D006864:Hydrogenase / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D045331:Photosystem I Protein Complex / Q000737:chemistry*; D013329:Structure-Activity Relationship; D046940:Synechococcus / Q000737:chemistry
chemical_list: D007506:Iron-Sulfur Proteins; D045331:Photosystem I Protein Complex; C118830:iron hydrogenase; D006864:Hydrogenase