Bioremediation of Chromium-Contaminated Groundwater Using Chromate Reductase from Pseudomonas putida: An In Silico Approach

Chromium is a toxic heavy metal abundantly present in the environment, specifically in groundwater. The groundwater in Saudi Arabia was assessed for heavy metal presence; chromium was detected at a high concentration in Madinah. Many researchers have used various bioprocesses over the last few decades to mitigate Cr(VI) toxicity. The genus Pseudomonas member Pseudomonas putida is widely dispersed in the natural environment. P. putida is chromate-resistant and has a high chromate reduction rate. Bioremediation procedures can eradicate the most potently toxic metal, Cr(VI), in water, air, and soil. Chromate reductase (ChrR) is a bacterial enzyme from P. putida that can be utilized in bioremediation to remove chromate from the environment in a cost-effective and environmentally safe approach. To comprehend the role of ChrR in reducing Cr(VI) to Cr(III), a thorough sequence analysis was followed by constructing models for wild-type and mutants by applying several homology modeling techniques. The protein structure quality of the generated models was evaluated, and the best model was adopted for further optimization by employing an energy minimization technique. Molecular docking studies investigated the intra-molecular interaction between wild-type and mutant ChrR and Cr(VI). Our study is a novel method for determining the 3D structure and interaction of ChrR with Cr(VI) to convert it to a less hazardous form (III). Additionally, it provides stable mutants: Arg83Trp, Gly124Ile, and His127Trp, with a high binding affinity for Cr(VI), which can be considered for protein engineering to produce stable and efficacious enzymes to reduce Cr(VI) to a less toxic form.