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. 2021 May 18;12:2927. doi: 10.1038/s41467-021-23248-z

Fig. 5. A mechanistic model of LysPG synthesis and translocation mediated by MprF.

Fig. 5

While each monomer in the homodimer may mediate the entire cycle of LysPG synthesis, translocation and release independently, the other monomer may also serve to stabilize the adjacent one in the optimal position (relative to lipid bilayer) for synthesis and translocation of LysPG. The cavities and Arg304–Glu280 pair are only shown in the active monomer and the other monomer is left out for clarity. State 0 represents a resting state of MprF. At State 1, the curved solid arrow indicates the nucleophilic attack of the PG head-group hydroxyl on the activated α-carbon of lysyl-tRNA and the dash arrow denotes the break of covalent bond between lysyl group and tRNA. At States 2 and 4, the dash arrows indicate the lateral diffusion of LysPG into and out of the cavities in RtMprF. Loading of LysPG into Cavity C leads to State 3 as observed in the RtMprF(DDM)-nanodisc structure. During the transition from State 3 to State 4, a channel connecting Cavity C and Cavity P may emerge transiently to facilitate translocation of LysPG. When the Cavity C in State 4 is refilled with a second LysPG molecule, both cavities are occupied by LysPG as observed in the RtMprF(GDN)-nanodisc structure (State 5). Further releasing of LysPG from Cavity P to the membrane leads to switching of State 5 to State 3.