A bioinorganic hybrid system based on bacterial surface display and biomimetic silicification for hydrogen production.

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.

A lead-specific binding protein, PbrR, and promoter pbr from the lead resistance operon, pbr, of Cupriavidus metallidurans CH34 was incorporated into E. coli in conjunction with an engineered downstream RFP (red fluorescence protein), which allowed for highly sensitive and selective whole-cell detection of lead ions. The subsequent display of PbrR on the E. coli cell surface permitted selective adsorption of lead ions from solution containing various heavy metal ions. The surface-engineered E. coli bacteria effectively protected Arabidopsis thaliana seed germination from the toxicity of lead ions at high concentrations. Engineering the E. coli bacteria harboring these lead-specific elements from the pbr operon may potentially be a valuable general strategy for biodetection and bioremediation of toxic heavy metal ions in the environment.