Mutations of methionine 444 interacting with T1Cu-coordinating amino acids affect the structure and function of multicopper oxidase CopA

Manganese is an essential trace element for humans, animals, and plants, but excessive amounts of manganese can cause serious harm to organisms. The biological manganese oxidation process mainly oxidizes Mn(II) through the secretion of unique manganese oxidase by manganese-oxidizing bacteria. The T1 Cu site of multicopper oxidase is the main site for substrate oxidation, and its role is to transfer electrons to TNC, where dioxygen reduction occurs. In this study, methionine (Met) No. 444 interacting with the T1Cu-coordinating amino acid in the multicopper oxidase CopA from Brevibacillus panacihumi MK-8 was mutated to phenylalanine (Phe) and leucine (Leu) by the enzyme. Based on the analysis of enzymatic properties and the structural model, the mutant protein M444F with 4.58 times the catalytic efficiency of the original protein CopA and the mutant protein M444L with 1.67 times the catalytic efficiency of the original protein CopA were obtained. The study showed that the manganese removal rate of the manganese-oxidizing engineered bacterium Rosetta-pET-copA^M444L cultured for 7 days was 88.87%, which was 10.77% higher than that of the original engineered bacterium. Overall, this study provides a possibility for the application of genetic engineering in the field of biological manganese removal.