Purification of Mutacin III from Group III Streptococcus mutans UA787 and Genetic Analyses of Mutacin III Biosynthesis Genes

Abstract

Previously, members of our group reported the isolation and characterization of mutacin II from Streptococcus mutans T8 and the genetic analyses of the mutacin II biosynthesis genes (J. Novak, P. W. Caufield, and E. J. Miller, J. Bacteriol. 176:4316–4320, 1994; F. Qi, P. Chen, and P. W. Caufield, Appl. Environ. Microbiol. 65:652–658, 1999; P. Chen, F. Qi, J. Novak, and P. W. Caufield, Appl. Environ. Microbiol. 65:1356–1360, 1999). In this study, we cloned and sequenced the mutacin III biosynthesis gene locus from a group III strain of S. mutans, UA787. DNA sequence analysis revealed eight open reading frames, which we designated mutR, -A, -A′,-B, -C, -D, -P, and-T. MutR bears strong homology with MutR of mutacin II, while MutA, -B, -C, -D, -P, and -T are counterparts of proteins in the lantibiotic epidermin group. MutA′ has 60% amino acid identity with MutA and therefore appears to be a duplicate of MutA. Insertional inactivation demonstrated that mutA is an essential gene for mutacin III production, while mutA′ is not required. Mutacin III was purified to homogeneity by using reverse-phase high-pressure liquid chromatography. N-terminal peptide sequencing of the purified mutacin III determined mutA to be the structural gene for prepromutacin III. The molecular mass of the purified peptide was measured by laser disorption mass spectrophotometry and found to be 2,266.43 Da, consistent with our supposition that mutacin III has posttranslational modifications similar to those of the lantibiotic epidermin.

The mutacins of Streptococcus mutans: regulation and ecology

“…The currently characterized lantibiotic mutacins include mutacin I (Qi et al, 2000), mutacin II (Novak et al, 1994), mutacin III/mutacin 1140 (these two mutacins have identical sequences: see Hillman et al, 1998;Qi et al, 1999b), mutacin B-NY266 (Mota-Meira et al, 1997), mutacin K8 (Robson et al, 2007), and mutacin Smb (Yonezawa & Kuramitsu, 2005). The term 'lantibiotic' refers to the characteristic dehydrated amino acids and intramolecular thioether bonds that create lanthionine and methyllanthionine residues within the bacteriocin molecule (Jung, 1991).…”

“…Of the mutacin gene clusters characterized to date, the mutacin I, II and III loci have each been shown to encode homologous Rgg-family transcription regulators referred to as mutR ( Fig. 1) (Chen et al, 1999;Qi et al, 1999b;. Though the entire mutacin 1140 locus has yet to be sequenced, a partial open reading frame annotated as ORF X was identified in the beginning of the published sequence (Hillman et al, 1998).…”

Cell density- and ComE-dependent expression of a group of mutacin and mutacin-like genes in Streptococcus mutans

“…Bacteriocin (mutacin) production is recognized as one of the virulence factors that contributes to this ecological switch. Two types of mutacins have been characterized in S. mutans: the lantibiotics and the nonlantibiotics (Novak et al, 1994;Qi et al, 1999Qi et al, , 2000Qi et al, , 2001. The lantibiotics, represented by mutacin I, II and III, have a killing spectrum against most of the Gram-positive bacteria.…”

Streptococcus rattusstrain BHT produces both a class I two-component lantibiotic and a class II bacteriocin

“…Caufield and associates characterised the lantibiotic mutacins I, II and III and the di‐peptide non‐lantibiotic mutacin IV [5–9]. In this laboratory, bacteriocin‐producing streptococci are initially categorized by assessing their inhibitory activity against nine indicator bacteria using bacteriocin P (production) typing[10].…”