Role of MurT C-Terminal Domain in the Amidation of Staphylococcus aureus Peptidoglycan

Fundacao para a Ciencia e a Tecnologia (FCT) through grants PTDC/FIS-NAN/ 0117/2014 and PTDC/BIA-MIC/31645/2017. project UID/Multi/04378/2019 (Unidade de Ciencias Biomoleculares Aplicadas-UCIBIO), funded by FCT/MCTES; project LISBOA-01-0145-FEDER-007660 (Microbiologia Molecular, Estrutural e Celular), funded by FEDER through COMPETE2020-Programa Operacional Competitividade e Internacionalizacao (POCI); national funds through FCT; by project ONEIDA (LISBOA-01-0145-FEDER-016417), cofunded by FEEI (Fundos Europeus Estruturais e de Investimento) from the Programa Operacional Regional Lisboa 2020; and by national funds from FCT. Funding was also provided by European Society of Clinical Microbiology and Infectious Diseases research grant 2015, awarded to R.G.S. B.V.G., T.A.F., and I.R.G. were supported by fellowships SFRH/BD/131623/2017 respectively. J.S.D. acknowledges the National NMR Network (PTNMR) and Infrastructure Project ROTEIRO/0031/2013-PINFRA/22161/2016 (cofinanced by FEDER through COMPETE 2020, POCI, PORL, and FCT through PIDDAC). Glutamate amidation, a secondary modification of the peptidoglycan, was first identified in Staphylococcus aureus. It is catalyzed by the protein products of the murT and gatD genes, which are conserved and colocalized in the genomes of most sequenced Gram-positive bacterial species. The MurT-GatD complex is required for cell viability, full resistance to β-lactam antibiotics, and resistance to human lysozyme and is recognized as an attractive target for new antimicrobials. Great effort has been invested in the study of this step, culminating recently in three independent reports addressing the structural elucidation of the MurT-GatD complex. In this work, we demonstrate through the use of nonstructural approaches the critical and multiple roles of the C-terminal domain of MurT, annotated as DUF1727, in the MurT-GatD enzymatic complex. This domain provides the physical link between the two enzymatic activities and is essential for the amidation reaction. Copurification of recombinant MurT and GatD proteins and bacterial two-hybrid assays support the observation that the MurT-GatD interaction occurs through this domain. Most importantly, we provide in vivo evidence of the effect of substitutions at specific residues in DUF1727 on cell wall peptidoglycan amidation and on the phenotypes of oxacillin resistance and bacterial growth. publishersversion published