Cyclic bacteriocins

Figure 4 Structural features and diversity of bacteriocins. Solution NMR structures are shown for (a) the lantibiotic actagardine (PDB code 1AJ1) the pedocin-like bacteriocins (b) curvacin A (PDB code 2A2B) and (c) leucocin A (PDB code 1CW6) (d) the A and B chain of the two-chain bacteriocin lactococcin G in DPC micelles (PDB codes 2JPJ and 2JPK) and the cyclic bacteriocins (e) subtilosin (PDB code 1AJ1) and (f) AS-48 (PDB code 1E68). Disulphide bonds and lanthionine linkages are shown in ball-and-stick. Chain termini are labelled N and C and the cyclisation points on the cyclic peptides are labelled with residue numbers.

Class II bacteriocins can be further divided into four groups based on structural features pediocin-like bacteriocins, two-peptide bacteriocins, cyclic bacteriocins and linear non-pediocin-like one-peptide bacteriocins. NMR has been used to characterise examples from each of these subgroups. 

Cyclic bacteriocins. At least seven bacteriocins discovered over recent years have been shown to have the unusual feature of a head-to-tail circular backbone.56 This post-translational modification is believed to stabilise the 3D structures of the peptides in a conformation needed for their membrane-disrupting function. 

Precursor protein that produces the cyclic trypsin inhibitor SFTI-1 Two-peptide bacteriocin plantaracin EF Lei4P... 

Prochloron spp. synthesize patellamides using a bacteriocin-like process. " The final patellamide structures are directly encoded on a precursor peptide, PatE. This linear, ribosomally encoded peptide must be modified and cleaved to yield heterocyclized, macrocyclized patellamides. In particular, the patellamides must be cut out of the precursor peptide from both their C- and N-termini, a property not yet observed in any other cyclic... 

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