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Sci Rep. 2017 Jan 6;7:39392. doi: 10.1038/srep39392.

Insights into the Mechanistic Basis of Plasmid-Mediated Colistin Resistance from Crystal Structures of the Catalytic Domain of MCR-1.

Author information

1
School of Cellular and Molecular Medicine, University of Bristol, Bristol BS8 1TD, UK.
2
Institute of Infection and Immunity, Cardiff University, Cardiff CF14 4XN, UK.
3
School of Chemistry, University of Bristol, Bristol BS8 1TS, UK.
4
Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Veterinary Medicine, China Agricultural University, Beijing, China.
5
Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, UK.
6
Department of Chemistry, University of Oxford, Oxford OX1 3TA, UK.
7
Department of Microbiology and Parasitology, Faculty of Medical Science, Naresuan University, Phitsanulok, 65000, Thailand.

Abstract

The polymixin colistin is a "last line" antibiotic against extensively-resistant Gram-negative bacteria. Recently, the mcr-1 gene was identified as a plasmid-mediated resistance mechanism in human and animal Enterobacteriaceae, with a wide geographical distribution and many producer strains resistant to multiple other antibiotics. mcr-1 encodes a membrane-bound enzyme catalysing phosphoethanolamine transfer onto bacterial lipid A. Here we present crystal structures revealing the MCR-1 periplasmic, catalytic domain to be a zinc metalloprotein with an alkaline phosphatase/sulphatase fold containing three disulphide bonds. One structure captures a phosphorylated form representing the first intermediate in the transfer reaction. Mutation of residues implicated in zinc or phosphoethanolamine binding, or catalytic activity, restores colistin susceptibility of recombinant E. coli. Zinc deprivation reduces colistin MICs in MCR-1-producing laboratory, environmental, animal and human E. coli. Conversely, over-expression of the disulphide isomerase DsbA increases the colistin MIC of laboratory E. coli. Preliminary density functional theory calculations on cluster models suggest a single zinc ion may be sufficient to support phosphoethanolamine transfer. These data demonstrate the importance of zinc and disulphide bonds to MCR-1 activity, suggest that assays under zinc-limiting conditions represent a route to phenotypic identification of MCR-1 producing E. coli, and identify key features of the likely catalytic mechanism.

PMID:
28059088
PMCID:
PMC5216409
DOI:
10.1038/srep39392
[Indexed for MEDLINE]
Free PMC Article

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