Nisin gene sequencing and inhibitory spectrum of nisin positive isolates The nine Lactocccus isolates that presented positive results for nis were identified as capable of producing a novel nisin variant. Their amino-acid sequence were diverse from to the other nisin variants already described (Figure 3). In all translated sequences the typical variation in nisin Z was identified: an asparagine

instead of a histidine in position 27 (Figure 3), as described previously [25, 56]. In addition, all isolates presented identical variations in their translated sequences when compared to a reference sequences of nisin (Figure 3): 1) in the leader peptide, an aspartic acid was replaced by an asparagine Dinaciclib in vitro in position -7; 2) except for GLc03, an isoleucine was replaced PF299 cost by a valine in position +4; and 3) a leucine was replaced by a valine in position +16 (Figure 3). Concerning the nisin leader peptide sequence, in the position -7, one negative-charged amino-acid (aspartic acid) was replaced by one uncharged amino-acid (asparagine). This same replacement also occurs in Nisin U1 (Figure 3). Indicating that this change selleck chemicals llc cannot interfere with the correct activity of the peptide. It is important to highlight two characteristics: 1) variations

in the sequence between positions -18 and -15 would interfere with nisin production, and 2) mutagenesis in Arg1- and Ala4- would affect cleavage of the leader peptide, resulting in a non-active nisin [52]. Sclareol However, the observed modification in the leader peptide of the translated sequences was not in these regions, indicating that nisin production and activity would not be affected in the tested isolates (Figure 3). Considering the mature peptide, in positions +4 and +16 of the nisin sequence, one neutral amino-acid (isoleucine and leucine respectively) was replaced by other neutral amino-acid (valina). The only described modification in the +4 region is

in nisin U (isoleucine replaced by lysine) [19]. The last variation and well know is in position +27, where one uncharged amino-acid (asparagine) is replaced by one positive electrically charge and basic amino-acid (histidin). This typical change for nisin Z was previously described as responsible for increasing its inhibitory spectrum due to its better diffusion capacity in culture media. It is common to observe variations in the amino-acid sequences of lantibiotics, including nisin, that then require proper characterization since they can interfere with the antimicrobial activity of these substances [18]. The observed variations in the translated nisin sequences have not been reported before, after consulting GenBank. Figure 3 Amino-acid sequences of a novel nisin variants deduced by the sequencing of nisin region from nine Lactococcus spp.