Hydrogen bond strength modulates the mechanical strength of ferric-thiolate bonds in rubredoxin |
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Authors: | Zheng Peng Takayama Shin-ichi J Mauk A Grant Li Hongbin |
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Institution: | Department of Chemistry, University of British Columbia, Vancouver, BC V6T 1Z1 Canada. |
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Abstract: | It has long been recognized that hydrogen bonds formed by protein backbone amides with cysteinyl S(γ) atoms play important roles in modulating the functional and structural properties of the iron-sulfur centers in proteins. Here we use single molecule atomic force microscopy, cyclic voltammetry, and protein engineering techniques to investigate directly how the strength of N-H···S(γ) hydrogen bonds in the secondary coordination sphere affects the mechanical stability of Fe(III)-thiolate bonds of rubredoxin. Our results show that the mechanical stability of Fe(III)-thiolate bonds in rubredoxin correlates with the strength of N-H···S(γ) hydrogen bonds as reflected by the midpoint reduction potential, providing direct evidence that N-H···S(γ) hydrogen bonds play important roles in modulating the mechanical and kinetic properties of the Fe(III)-thiolate bonds of iron-sulfur proteins and corroborating the important roles of the protein environment in tuning the properties of metal-thiolate bonds. |
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