The Acidithiobacillus ferroxidanse bacterium plays an important role in the bioleaching process of Uranium. The rusticyanin protein is the second most important component in the electron transport chain in the membrane of the Acidithiobacillus ferroxidnase bacterium. This protein belongs to the large family of copper blue proteins. A change in protein structure can affect protein function. The protein sequence rusticyanin 23270 was derived from UniProtKB database. A suitable model for modeling was prepared from Swiss model server and the best protein model was made with Moedller software. The His143Leu mutation was developed using the Pymol software in the protein and the effect of the mutation on the stability of the protein structure was investigated using the analysing results of molecular dynamics simulation on the wild-type and mutant protein. The values RMSD and RMSF for wild-type and mutant are 0.025 and 0.021 nm respectively. The amount of Rg in mutant protein is 0.163 nm is lower than in the wild-type . His143Leu mutation in the rusticyanin 23270 protein does not affect the secondary structure protein and slightly increases the folding and stability of the tertiary structure.