Mutual influence of secondary and key drug‐resistance mutations on catalytic properties and thermal stability of TEM‐type β‐lactamases

• Published in: FEBS open bio 2018-01, Vol.8 (1), p.117-129
• Main Authors: Grigorenko, Vitaly, Uporov, Igor, Rubtsova, Maya, Andreeva, Irina, Shcherbinin, Dmitrii, Veselovsky, Alexander, Serova, Oksana, Ulyashova, Maria, Ishtubaev, Igor, Egorov, Alexey
• Format: Article
• Language: English
• Subjects: antibiotic resistance; Antibiotics; Computer applications; Deoxyribonucleic acid; DNA; Drug resistance; drug resistance mutations; E coli; Enzymes; Gram-negative bacteria; High temperature; Hydrogen bonding; Lysine; molecular dynamics; Mutagenesis; Mutation; Protein structure; Proteins; recombinant TEM‐type β‐lactamases; Secondary structure; Site-directed mutagenesis; Thermal stability
• ISSN: 2211-5463; 2211-5463
• DOI: 10.1002/2211-5463.12352

Highly mutable β‐lactamases are responsible for the ability of Gram‐negative bacteria to resist β‐lactam antibiotics. Using site‐directed mutagenesis technique, we have produced in vitro a number of recombinant analogs of naturally occurring TEM‐type β‐lactamases, bearing the secondary substitution Q39K and key mutations related to the extended‐spectrum (E104K, R164S) and inhibitor‐resistant (M69V) β‐lactamases. The mutation Q39K alone was found to be neutral and hardly affected the catalytic properties of β‐lactamases. However, in combination with the key mutations, this substitution resulted in decreased KM values towards hydrolysis of a chromogenic substrate, CENTA. The ability of enzymes to restore catalytic activity after exposure to elevated temperature has been examined. All double and triple mutants of β‐lactamase TEM‐1 bearing the Q39K substitution showed lower thermal stability compared with the enzyme with Q39 intact. A sharp decrease in the stability was observed when Q39K was combined with E104K and M69V. The key R164S substitution demonstrated unusual ability to resist thermal inactivation. Computer analysis of the structure and molecular dynamics of β‐lactamase TEM‐1 revealed a network of hydrogen bonds from the residues Q39 and K32, related to the N‐terminal α‐helix, towards the residues R244 and G236, located in the vicinity of the enzyme's catalytic site. Replacement of Q39 by lysine in combination with the key drug resistance mutations may be responsible for loss of protein thermal stability and elevated mobility of its secondary structure elements. This effect on the activity of β‐lactamases can be used as a new potential target for inhibiting the enzyme. We investigated the effects of mutations on the activity and stability of TEM‐type β‐lactamases conferring resistance to β‐lactam antibiotics. The secondary mutation Q39K in combination with key mutations (E104K, R164S, M69V) resulted in loss of thermal stability, while a single mutation, R164S, showed the opposite effect. Computer modeling revealed a hydrogen bond network from Q39 and K32 towards R244 and G236 located in the vicinity of the active site.