Crystal Structure of the Periplasmic Component of a Tripartite Macrolide-Specific Efflux Pump
- Crystal Structure of the Periplasmic Component of a Tripartite Macrolide-Specific Efflux Pump
- Soohwan Yum; Yongbin Xu; Shunfu Piao; Se-Hoon Sim; Hong-Man Kim; Wol-Soon Jo; Kyung-Jin Kim; Hee-Seok Kweon; Min-Ho Jeong; 전혜성; Kangseok Lee; Nam-Chul Ha
- multidrug efflux pump; MacA; TolC; AcrA; Gram-negative bacteria
- Issue Date
- Journal of molecular biology
- VOL 387, NO 5, 1286-1297
- In Gram-negative bacteria, type I protein secretion systems and tripartite
drug efflux pumps have a periplasmic membrane fusion protein (MFP) as
an essential component. MFPs bridge the outer membrane factor and an
inner membrane transporter, although the oligomeric state ofMFPs remains
unclear. The most characterized MFP AcrA connects the outer membrane
factor TolC and the resistance–nodulation–division-type efflux transporter
AcrB, which is a major multidrug efflux pump in Escherichia coli. MacA is
the periplasmic MFP in the MacAB–TolC pump, where MacB was characterized
as a macrolide-specific ATP-binding-cassette-type efflux transporter.
Here, we report the crystal structure of E. coli MacA and the experimentally
phased map of Actinobacillus actinomycetemcomitans MacA, which reveal a
domain orientation of MacA different from that of AcrA. Notably, a
hexameric assembly of MacA was found in both crystals, exhibiting a
funnel-like structure with a central channel and a conical mouth. The
hexameric MacA assembly was further confirmed by electron microscopy
and functional studies in vitro and in vivo. The hexameric structure of MacA
provides insight into the oligomeric state in the functional complex of the
drug efflux pump and type I secretion system.
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