Structural Insights and the Surprisingly Low Mechanical Stability of the Au–S Bond in the Gold-Specific Protein GolB

Wei Wei†‡, Yang Sun§, Mingli Zhu†‡, Xiangzhi Liu†‡, Peiqing Sun†‡, Feng Wang^∥, Qiu Gui‡, Wuyi Meng^∥, Yi Cao^*§, and Jing Zhao^*†‡

^†State Key Laboratory of Coordination Chemistry, Institute of Chemistry and BioMedical Sciences, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Chemistry for Life Sciences, ^‡State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, and ^§Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructure, Department of Physics, Nanjing University, Nanjing 210093, China

^∥ Elias James Corey Institute of Biomedical Research, Wuxi Biortus Biosciences Co., Ltd, Jiangyin, 214437, China

J. Am. Chem. Soc., Article ASAP

DOI: 10.1021/jacs.5b09895

Abstract

The coordination bond between gold and sulfur (Au–S) has been widely studied and utilized in many fields. However, detailed investigations on the basic nature of this bond are still lacking. A gold-specific binding protein, GolB, was recently identified, providing a unique opportunity for the study of the Au–S bond at the molecular level. We probed the mechanical strength of the gold–sulfur bond in GolB using single-molecule force spectroscopy. We measured the rupture force of the Au–S bond to be 165 pN, much lower than Au–S bonds measured on different gold surfaces (∼1000 pN). We further solved the structures of apo-GolB and Au(I)–GolB complex using X-ray crystallography. These structures showed that the average Au–S bond length in GolB is much longer than the reported average value of Au–S bonds. Our results highlight the dramatic influence of the unique biological environment on the stability and strength of metal coordination bonds in proteins.

http://dx.doi.org/10.1021/jacs.5b09895