The nature of these compounds

is still unknown, but divalent anions such as sulfates are suspected. As seen in previous work with other mutacins, purification yields were low (Table 1) and additional chromatographic steps will be necessary to improve yields and purity. The higher concentration of methanol used to recover mutacin D-123.1 suggests that the peptide is more hydrophobic than mutacin F-59.1. SBE-��-CD nmr collected samples of pure mutacin D-123.1 were very viscous because they probably retain part of the polymeric sugars from the agarose. However, with the methods used here, sufficient amounts of the substances were collected to carry out a preliminary characterisation of the peptides but the evaluation of their antibacterial LY411575 mw spectrum was somewhat Epacadostat in vitro restricted. The sequence of mutacin F-59.1 (25 residues) was shorter than the

generally recognised size for pediocin-like bacteriocins which is between 37 and 48 residues [2, 13]. This may be due to peptidase activity of the strain. Fifty three peptidases or peptidase homologues are found in the genome of S. mutans UA159 using the MEROPS database [17, 18]http://​merops.​sanger.​ac.​uk. The pediocin-like bacteriocin sequence could thus be a substrate in its 25th position for many of these peptidases. MALDI-TOF MS analysis revealed a major peak with an isotopic mass [M+H]+ of 2720 Da for mutacin F-59.1 (Figure 4). This mass represents the lowest reported mass for an active naturally-produced

pediocin-like bacteriocin after the study of Bhunia et al. [19]. The length of mutacin F-59.1 was sufficient to confer antimicrobial activity against several bacterial genera including Bacillus spp., Enterococcus spp., Lactococcus spp., Micrococcus spp., Listeria spp., and Streptococcus spp. (Table 2). Salvucci et al. [20] Dipeptidyl peptidase reported activity of short peptides derived from the NH2-terminus of enterocin CRL35 and other class IIa bacteriocins, suggesting that the C-terminus of pediocin-like bacteriocins is not essential for their inhibitory activity. Also, an active antimicrobial region in the NH2-terminus of this class of bacteriocin was identified by a bioinformatic approach [21]. The C-terminus section is known to confer specificity in the activity spectra of class IIa bacteriocins and to interact with their cognate immunity proteins [22]. Pediocin-like bacteriocins are unstructured in an aqueous solution and become structured when in contact with membrane-mimicking entities [2]. The electrostatic distribution along the molecule is highly polarized with most of the cationic residues concentrated in the N-terminal region.

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