Broad‐spectrum antimicrobial peptide resistance by MprF‐mediated aminoacylation and flipping of phospholipids

Abstract

SummaryBacteria are frequently exposed to cationic antimicrobial peptides (CAMPs) from eukaryotic hosts (host defence peptides) or from prokaryotic competitors (bacteriocins). However, many bacteria, among them most of the major human pathogens, achieve CAMP resistance by MprF, a unique enzyme that modifies anionic phospholipids with L-lysine or L-alanine thereby introducing positive charges into the membrane surface and reducing the affinity for CAMPs. The lysyl or alanyl groups are derived from aminoacyl tRNAs and are usually transferred to phosphatidylglycerol (PG). Recent studies with MprF from Staphylococcus aureus demonstrated that production of Lys-PG only leads to CAMP resistance when an additional flippase domain of MprF is present that translocates Lys-PG and exposes it at the outer leaflet of the membrane. Thus, MprF exerts two specific functions that have hardly been found in other bacterial proteins. MprF proteins are crucial virulence factors of many human pathogens, which recommends them as targets for new anti-virulence drugs. Intriguingly, specific point mutations in mprF cause resistance to the CAMP-like antibiotic daptomycin in a yet unclear way that may involve altered Lys-PG synthesis and/or Lys-PG flipping capacities. Thus, a thorough characterization of MprF domains and functions will help to unravel how bacteria maintain and protect their cytoplasmic membranes.

A Genetic Screen in Myxococcus xanthus Identifies Mutants That Uncouple Outer Membrane Exchange from a Downstream Cellular Response

“…The OmrA protein has significant sequence homology to Pfam PF03706 (UPF0104) (E value, 1.7eϪ38). The best-characterized PF03706 family mem- ber is MprF from Staphylococcus aureus, where this domain resides in the cytoplasmic membrane and has phospholipid flippase activity (24). Consistent with a PF03706 designation, OmrA, like other family members, was predicted to contain eight transmembrane helices (TMHMM, version 2.0) (25) (Fig.…”

“…Insights into how cells respond to OME can be gleaned from (24). The MprF PF09924 domain (OmrB) catalyzes the synthesis of lysyl-phosphatidylglycerol from lysyltRNA and phosphatidylglycerol precursors.…”

“…5). Within the Pfam database (July 2014) (26), PF03706 was most frequently found as a single-domain protein (3,567 homologs); its second most frequent protein form consisted of an architecture where PF03706 was fused to a domain called DUF2156 (PF09924; 962 homologs), as found in MprF (24). To investigate whether other proteins may function in an OmrA pathway, we searched the M. xanthus DK1622 genome for ORFs that contained PF09924 (27).…”

Resistencia a antibióticos de última línea en cocos Gram positivos: la era posterior a la vancomicina

“…Esta es una enzima bifuncional que se encarga de la adición de lisina (aminoácido de carga positiva) a residuos de fosfatidilglicerol en la capa interna de la membrana celular, formando lisilfosfatidilglicerol (L-FG), y de la translocación de L-FG desde la capa interna hacia la capa externa de la membrana (actividad de flipasa) (93)(94)(95). En cepas de S. aureus resistentes a la daptomicina se han descrito diversas mutaciones en el mprF (94) que parecen incrementar la actividad de esta enzima, contribuyendo al incremento de la carga positiva de la superficie celular (94)(95)(96).…”

“…Esta es una enzima bifuncional que se encarga de la adición de lisina (aminoácido de carga positiva) a residuos de fosfatidilglicerol en la capa interna de la membrana celular, formando lisilfosfatidilglicerol (L-FG), y de la translocación de L-FG desde la capa interna hacia la capa externa de la membrana (actividad de flipasa) (93)(94)(95). En cepas de S. aureus resistentes a la daptomicina se han descrito diversas mutaciones en el mprF (94) que parecen incrementar la actividad de esta enzima, contribuyendo al incremento de la carga positiva de la superficie celular (94)(95)(96). El operón dltABC, responsable de la adición de D-alanina a los ácidos teicoicos (lo que aumenta la carga positiva de la membrana), también se ha relacionado con la reducción de la sensibilidad a la daptomicina (97) y, por último, las mutaciones puntuales en los genes rpoB y rpoC (que codifican para las subunidades ß y ß' de la ARN polimerasa, respectivamente), se han asociado, igualmente, con la aparición de la resistencia a la daptomicina en S. aureus (92,98).…”