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

• DOI: 10.1021/jacs.5b09895
• Publication Date: 2015-11-13T14:44:35Z
• Authors: Wei Wei; Yang Sun; Mingli Zhu; Xiangzhi Liu; Peiqing Sun; Feng Wang; Qiu Gui; Wuyi Meng; Yi Cao; Jing Zhao
• Keywords: Models, Molecular; Salmonella typhimurium; 0301 basic medicine; 03 medical and health sciences; Protein Stability; Metalloproteins; Gold; Crystallography, X-Ray; Sulfur; Mechanical Phenomena

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.