Elucidation of the CadA Protein 3D Structure and Affinity for Metals

The mitigation of cadmium (Cd) pollution, a significant ecological threat, is of paramount importance. Pseudomonas aeruginosa harbors 2 Cd resistance genes, namely, cadR and cadA. Presently, our focus is on the identification and characterization of the cation-transporting P-type ATPase (cadA) in Pseudomonas aeruginosa BC15 through in silico methods. The CadA protein and its binding capacities remain poorly understood, with no available structural elucidation. The presence of the cadA gene in P aeruginosa was confirmed, showing a striking 99% sequence similarity with both P aeruginosa and P putida. Phylogenetic analysis unveiled the evolutionary relationship between CadA protein sequences from various Pseudomonas species. Physicochemical analysis demonstrated the stability of CadA, revealing a composition of 690 amino acids, a molecular weight of 73 352.85, and a predicted isoelectric point (PI) of 5.39. Swiss-Model homology modelling unveiled a 33.73% sequence homology with CopA (3J09), and the projected structure indicated that 89.3% of amino acid residues were situated favourably within the Ramachandran plot, signifying energetic stability. Notably, the study identified metal-binding sites in CadA, namely, H3, C30, C32, C35, H48, C89, and C106. Docking studies revealed a higher efficiency of Cd binding with CadA compared to other heavy metals. This underscores the crucial role of N-terminal cysteine residues in Cd removal. It is evident that CadA of P aeruginosa BC15 plays a crucial role in Cd tolerance, rendering it a potential microorganism for Cd toxicity bioremediation. The structural and functional elucidation of CadA, facilitated by this study, holds promise for advancing cost-effective strategies in the remediation of cadmium-contaminated environments.