The study of the role of mutations M182T and Q39K in the TEM-72 β-lactamase structure by the molecular dynamics method

Synthesis of β-lactamases is one of the common mechanisms of bacterial resistance to β-lactam antibiotics such as penicillins and cephalosporins. The widespread use of antibiotics resulted in appearance of numerous extended-spectrum β-lactamase variants or inhibitor-resistant β-lactamases. In TEM type β-lactamases mutations of 92 residues have been described. Several mutations are functionally important and they determine the extended substrate specificity. However, roles of the most so-called associated mutations, located far from the active site, remain unknown. We have investigated the role of associated mutations in structure of β-lactamase TEM-72, which contains two key mutations (G238S, E240K) and two associated mutations (Q39K, M182T) by means of molecular dynamics simulation. Appearance of the key mutations (in 238 and 240 positions) caused destabilization of the protein globule, characterized by increased mobility of amino acid residues. Associated mutations (Q39K, M182T) exhibited opposite effect on the protein structure. The mutation M182T stabilized, while the mutation Q39K destabilized the protein. It appears that the latter mutation promoted optimization of the conformational mobility of β-lactamase and may influence the enzyme activity.