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Updated: Jun 23, 2026

Production, Crystallization and Structure Determination of C. difficile PPEP-1 via Microseeding and Zinc-SAD
Published on: December 30, 2016
Crystallization of a pentapeptide-repeat protein by reductive cyclic pentylation of free amines with glutaraldehyde
Matthew W Vetting1, Subray S Hegde, John S Blanchard
1Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA. vetting@aecom.yu.edu
Abstract:
The pentapeptide-repeat protein EfsQnr from Enterococcus faecalis protects DNA gyrase from inhibition by fluoroquinolones. EfsQnr was cloned and purified to homogeneity, but failed to produce diffraction-quality crystals in initial crystallization screens. Treatment of EfsQnr with glutaraldehyde and the strong reducing agent borane-dimethylamine resulted in a derivatized protein which produced crystals that diffracted to 1.6 A resolution; their structure was subsequently determined by single-wavelength anomalous dispersion. Analysis of the derivatized protein using Fourier transform ion cyclotron resonance mass spectrometry indicated a mass increase of 68 Da per free amino group. Electron-density maps about a limited number of structurally ordered lysines indicated that the modification was a cyclic pentylation of free amines, producing piperidine groups.
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