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J Struct Biol. 2001 Oct;136(1):81-8.

Lipid-layer crystallization and preliminary three-dimensional structural analysis of AcrA, the periplasmic component of a bacterial multidrug efflux pump.

Author information

1
Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Mailstop Donner, Berkeley, CA 94720, USA. AJAvila-Sakar@lbl.gov

Abstract

The multidrug efflux complex AcrAB-TolC confers intrinsic drug resistance in Escherichia coli by pumping antibiotics out of the cell. We determined a low-resolution (20 A) structure of AcrA, the periplasmic component, by electron crystallography. Expressed with a His-tag at its carboxyl-terminus, the protein bound to lipid layers containing the nickel-chelating phospholipid DOGS-NTA. Under the lipid layers, AcrA crystallized in layer group P2(1)22, with a unit cell size of 157 by 95 A and a thickness of about 100 A. The four asymmetric units in the unit cell are organized into what appears to be two rings, each with a central opening of 30 A in diameter. Within each ring, the density can be interpreted as following a pseudo-helical path, approximately 210 A long. This length matches that of monomeric AcrA in solution, previously estimated by light scattering and hydrodynamic measurements. On one side the density has a tubular shape, with a thickness of about 25 A, while on the other side the densities of the upper and lower parts of the pseudo-helical path are fused into a shield.

PMID:
11858709
DOI:
10.1006/jsbi.2001.4418
[Indexed for MEDLINE]

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