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Bacteriocins produced by latic acid bacteria are potent antimicrobial compounds that are active against closely related bacteria. The NMR solution structure of the 111-amino acid immunity protein for carnobacteriocin B2 (ImB2) is reported.

A paramagnetic copper-chelated lipid is used to enhance the spin-lattice relaxation and thereby speed up solid-state NMR measurements. The results have shown a 6.2-fold speed increase and a 2.7-fold improvement in signal-to-noise ratio for solid-state NMR experiments under magic-angle spinning and static conditions.

Multidimensional NMR studies on subtilosin A, a bacteriocin from Bacillus subtilis, are carried out to determine the complete primary and three-dimensional solution structure of peptide. Results depicted a cyclized peptide backbone with three cross-links formed between the sulfurs of Cys13, Cys 7, and Cys4 and the alpha-positions of Phe22, Thr28 and Phe31 that are showing L form of stereochemistry.

Bacteriocins produced by lactic acid bacteria are potent antimicrobial compounds which are active against closely related bacteria. Producer strains are protected against the effects of their cognate bacteriocins by immunity proteins that are located on the same genetic locus and are coexpressed with the gene encoding the bacteriocin. Several structures are available for class IIa bacteriocins; however, to date, no structures are available for the corresponding immunity proteins. We report here the NMR solution structure of the 111-amino acid immunity protein for carnobacteriocin B2 (ImB2). ImB2 folds into a globular domain in aqueous solution which contains an antiparallel four-helix bundle. Extensive packing by hydrophobic side chains in adjacent helices forms the core of the protein. The C-terminus, containing a fifth helix and an extended strand, is held against the four-helix bundle by hydrophobic interactions with helices 3 and 4. Most of the charged and polar residues in the protein face the solvent. Helix 3 is well-defined to residue 55, and a stretch of nascent helix followed by an unstructured loop joins it to helix 4. No interaction is observed between ImB2 and either carnobacteriocin B2 (CbnB2) or its precursor. Protection from the action of CbnB2 is only observed when ImB2 is expressed within the cell. The loop between helices 3 and 4, and a hydrophobic pocket which it partially masks, may be important for interaction with membrane receptors responsible for sensitivity to class IIa bacteriocins. [ABSTRACT FROM AUTHOR]