Preprint Communication Version 1 Preserved in Portico This version is not peer-reviewed

Spermidine Binding to the Acetinobacter baumannii Efflux Protein AceI Observed by Near-UV Synchrotron Radiation Circular Dichroism Spectroscopy

Version 1 : Received: 6 January 2022 / Approved: 10 January 2022 / Online: 10 January 2022 (12:19:07 CET)

How to cite: Patching, S. Spermidine Binding to the Acetinobacter baumannii Efflux Protein AceI Observed by Near-UV Synchrotron Radiation Circular Dichroism Spectroscopy. Preprints 2022, 2022010108 (doi: 10.20944/preprints202201.0108.v1). Patching, S. Spermidine Binding to the Acetinobacter baumannii Efflux Protein AceI Observed by Near-UV Synchrotron Radiation Circular Dichroism Spectroscopy. Preprints 2022, 2022010108 (doi: 10.20944/preprints202201.0108.v1).

Abstract

The aim of this work was to test polyamines as potential natural substrates of the Acinetobacter baumannii chlorhexidine efflux protein AceI using near-UV synchrotron radiation circular dichroism (SRCD) spectroscopy. The Gram-negative bacterium A. Baumannii is a leading cause of hospital-acquired infections and an important foodborne pathogen. A. Baumannii strains are becoming increasingly resistant to antimicrobial agents, including the synthetic antiseptic chlorhexidine. AceI was the founding member of the recently recognised PACE family of bacterial multidrug efflux proteins. Using the plasmid construct pTTQ18-aceI(His6) containing the A. Baumannii aceI gene directly upstream from a His6-tag coding sequence, expression of AceI(His6) was amplified in E. coli BL21(DE3) cells. Near-UV (250-340 nm) SRCD measurements were performed on detergent-solubilised and purified AceI(His6) at 20 °C. Sample and SRCD experimental conditions were identified that detected binding of the triamine spermidine to AceI(His6). In a titration with spermidine (0-10 mM) this binding was saturable and fitting of the curve for the change in signal intensity produced an apparent binding affinity (KD) of 3.97 +/- 0.45 mM. These SRCD results were the first experimental evidence obtained for polyamines as natural substrates of PACE proteins.

Keywords

Acinetobacter baumannii; antimicrobial resistance; circular dichroism spectroscopy; efflux protein; efflux pump; foodborne pathogen; hospital-acquired infection; polyamine

Subject

LIFE SCIENCES, Molecular Biology

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