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Updated: Jun 28, 2026

From Constructs to Crystals – Towards Structure Determination of β-barrel Outer Membrane Proteins
Published on: July 4, 2016
Crystal structure of a LysR regulator reveal an unconventional effector pocket from Acinetobacter baumannii
Qingsong Lu1, Bowen Hu1, Yong Yu1
1School of Life Sciences and Medical Engineering, Anhui University, Hefei, 230601, PR China.
Abstract:
Acinetobacter baumannii is a multidrug-resistant pathogen, and rising chlorhexidine tolerance threatens infection control. chlorhexidine induces the AceI efflux pump via the transcriptional regulator AceR, but the structural basis of effector recognition by AceR is unknown. Here, we report the 1.82 Å crystal structure of the AceR effector-binding domain (EBD) and its co-crystal structure with spermidine, a physiological substrate. A clear spermidine density appeared at the homodimer interface, where the ligand is symmetrically coordinated by both protomers-an arrangement seldom seen in LTTR family. Site-directed mutagenesis combined with isothermal titration calorimetry (ITC) demonstrates that amino acid substitutions at this interface impair CHX binding, confirming its physiological relevance. These results reveal an unconventional ligand-binding site at the AceR homodimer interface, expanding the LTTR regulatory paradigm and identifying a novel pocket.
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