Author/Authors :
Chang, Qingli th e Second Affiliated Hospital and Yuying Children’s Hospital - Wenzhou Medical University, China , Wu, Chongyang th e Second Affiliated Hospital and Yuying Children’s Hospital - Wenzhou Medical University, China , Lin, Chaoqing th e Second Affiliated Hospital and Yuying Children’s Hospital - Wenzhou Medical University, China , Li, Peizhen School of Laboratory Medicine and Life Science - Institute of Biomedical Informatics - Wenzhou Medical University, China , Zhang, Kaibo School of Medicine and Health - Lishui University, China , Xu, Lei School of Laboratory Medicine and Life Science - Institute of Biomedical Informatics, Wenzhou Medical University, China , Liu, Yabo School of Laboratory Medicine and Life Science - Institute of Biomedical Informatics - Wenzhou Medical University, China , Lu, Junwan School of Medicine and Health - Lishui University, China , Cheng, Cong School of Medicine and Health - Lishui University, China , Bao, Qiyu th e Second Affiliated Hospital and Yuying Children’s Hospital - Wenzhou Medical University, China , Hu, Yunliang th e Second Affiliated Hospital and Yuying Children’s Hospital - Wenzhou Medical University, China , Lu, Shunfei School of Medicine and Health - Lishui University, China , Li, Jinsong School of Medicine and Health - Lishui University, China
Abstract :
In order to study the relationship between the structure and function of AmpG, structure, site-specific mutation, and gene complementary experiments have been performed against the clinical isolates of Pseudomonas aeruginosa. We found that there are 51 nucleotide variations at 34 loci over the ampG genes from 24 of 35 P. aeruginosa strains detected, of which 7 nucleotide variations resulted in amino acid change. The ampG variants with the changed nucleotides (amino acids) could complement the function of ampG deleted PA01 (PA01ΔG). The ampicillin minimum inhibitory concentration (MIC) of PA01ΔG complemented with 32 ampG variants was up to 512 μg/ml, similar to the original PA01 (P. aeruginosa PA01). Furthermore, site-directed mutation of two conservative amino acids (I53 and W90) showed that when I53 was mutated to 53S or 53T (I53S or I53T), the ampicillin MIC level dropped drastically, and the activity of AmpC β-lactamase decreased as well. By contrast, the ampicillin MIC and the activity of AmpC β-lactamase remained unchanged for W90R and W90S mutants. Our studies demonstrated that although nucleotide variations occurred in most of the ampG genes, the structure of AmpG protein in clinical isolates is stable, and conservative amino acid is necessary to maintain normal function of AmpG.
