Evolutionary Trajectory of the Tet(X) Family: Critical Residue Changes towards High-Level Tigecycline Resistance
Chao‐Yue Cui, He Qian, Qiu-Lin Jia, Cang Li, Chong Chen, Xiao-Ting Wu, Xiaojing Zhang, Zhuo-Yu Lin, Zi‐Jian Zheng, Xiao‐Ping Liao, Barry N. Kreiswirth, Yahong Liu, Liang Chen, Jian Sun
Abstract
The newly emerged tigecycline-inactivating enzymes Tet(X3) and Tet(X4), which are associated with high-level tigecycline resistance, demonstrated significantly higher activities in comparison to that of the prototypical Tet(X) enzyme, threatening the clinical efficacy of tigecycline as a last-resort antibiotic to treat multidrug-resistant (MDR) Gram-negative bacterial infections. However, the molecular mechanisms leading to high-level tigecycline resistance remain elusive. Here, we identified 5 key residue changes that lead to enhanced Tet(X) activity through domain swapping and site-directed mutagenesis. Instead of direct involvement with substrate binding or catalysis, these residue changes indirectly alter the conformational dynamics and allosterically affect enzyme activities. These findings further broaden the understanding of the structural characteristics and functional evolution of Tet(X) and provide a basis for the subsequent screening of specific inhibitors and the development of novel tetracycline antibiotics.