National Center for
2LA0: Trn- peptide of the two-component bacteriocin Thuricin CD
The 3D structure of thuricin CD, a two-component bacteriocin with cysteine sulfur to alpha-carbon cross-links
J. Am. Chem. Soc. (2011) 133 p.7680-7683
Thuricin CD is an antimicrobial factor that consists of two peptides, Trn-alpha and Trn-beta, that exhibit synergistic activity against drug resistant strains of Clostridium difficile. Trn-alpha and Trn-beta each possess three sulfur to alpha-carbon thioether bridges for which the stereochemistry is unknown. This report presents the three-dimensional solution structures of Trn-alpha and Trn-beta. Structure calculations were performed for the eight possible stereoisomers of each peptide based on the same NMR data. The structure of the stereoisomer that best fit the experimental data was chosen as the representative structure for each peptide. It was determined that Trn-alpha has L-stereochemistry at Ser21 (alpha-R), L-stereochemistry at Thr25 (alpha-R), and D-stereochemistry at Thr28 (alpha-S) (an LLD isomer). Trn-beta was also found to be the LLD isomer, with L-stereochemistry at Thr21 (alpha-R), L-stereochemistry at Ala25 (alpha-R), and D-stereochemistry at Tyr28 (alpha-S).