Catalyzes the transfer of a lysyl group from L-lysyl- tRNA(Lys) to membrane-bound phosphatidylglycerol (PG), which produces lysylphosphatidylglycerol (LPG), a major component of the bacterial membrane with a positive net charge. LPG synthesis contributes to bacterial virulence as it is involved in the resistance mechanism against cationic antimicrobial peptides (CAMP) produces by the host's immune system (defensins, cathelicidins) and by the competing microorganisms (bacteriocins). In fact, the modification of anionic phosphatidylglycerol with positively charged L-lysine results in repulsion of the peptides. Consequently, mprF is shown to affect resistance and susceptibility to moenomycin and vancomycin, resistance to human defensins (HNP1-3) and evasion of oxygen-independent neutrophil killing and susceptibility to methicillin, oxacillin, bacitracin, gentamicin, beta-lactams and synthetic peptides (hBD3, CAP18) and other cationic antimicrobial peptides.