The Molecular Mechanisms Underlying Hidden Phenotypic Variation among Metallo-β-Lactamases. Issue 6 (15th March 2019)

• Record Type: Journal Article
• Authors: Socha, Raymond D.; Chen, John; Tokuriki, Nobuhiko
• Is Part Of: Journal of molecular biology. Volume 431:Issue 6(2019)
• Page Start: 1172
• Page End: 1185
• Publication Date: 2019-03-15
• Subjects: HGT horizontal gene transfer -- MBL metallo-β-lactamase -- MIC minimum inhibitory concentration -- CAI codon adaptation index; Phenotypic variation -- Metallo-beta-lactamase -- Genetic incompatibility -- Protein expression -- Horizontal gene transfer; Molecular biology -- Periodicals; Biology -- Periodicals; Biochemistry -- Periodicals; Bacteriology -- Periodicals; Molecular Biology -- Periodicals; Biochemistry -- Periodicals; Biologie moléculaire -- Périodiques; Biologie -- Périodiques; Biochimie -- Périodiques; Moleculaire biologie; Biochemistry; Biology; Molecular biology; Periodicals; 572.805
• DOI: 10.1016/j.jmb.2019.01.041
• Languages: English
• ISSNs: 0022-2836

Abstract

Abstract: Genetic variation among orthologous genes has been largely formed through neutral genetic drift while maintaining the functional role of these genes. However, because the evolution of gene occurs in the context of each host organism, their sequence changes are also associated with adaptation to a specific environment. Thus, genetic variation can create critical phenotypic variation, particularly when genes are transferred to a new host by horizontal gene transfer. Unveiling "hidden phenotypic variation" is particularly important for genes that confer resistance to antibiotics. However, our understanding of the molecular mechanisms that underlie phenotypic variation remains limited. Here we sought to determine the extent of phenotypic variation in the B1 metallo-β-lactamase (MBL) family and its molecular basis by systematically characterizing eight MBL orthologs, including NDM-1 and VIM-2 and IMP-1. We found that these MBLs confer diverse levels of resistance. The phenotypic variation cannot be explained by variation in catalytic efficiency alone; rather, it is the combination of the catalytic efficiency and abundance of functional periplasmic enzyme that best predicts the observed variation in resistance. The level of functional periplasmic expression varied dramatically between MBL orthologs. This was the result of changes at multiple levels of each ortholog's: (1) quantity of mRNA, (2) amount of MBL expressed, and (3) efficacy of functional enzyme translocation to the periplasm. Overall, it is the interaction between each gene and the host's underlying cellular processes (transcription, translation, and translocation) that determines MBL genetic incompatibility through horizontal gene transfer. These host-specific processes may constrain the effective spread and deployment of MBLs to certain host species and could explain the current observed distribution bias. Graphical abstract: Unlabelled Image Highlights: Genetic variation among orthologous metallo-β-lactamases underlies substantial phenotypic variation for conferring diverse levels of antibiotic resistance. The variation in antibiotic resistance is caused by variation in functional protein expression rather than variation in catalytic efficiency. Each step of protein production, transcription, translation, and translocation, is responsible for the variation in functional protein expression. Genetic variation may play an important role in gene compatibility/incompatibility of horizontal gene transfer. The dissemination of antibiotic resistance genes may be strongly biased by their genotypes.