Lantibiotics are biologically active
peptides which contain the
thioether amino acid lanthionine as well as several other modified
amino acids. They can be broadly divided into two groups on the basis of their structures: type-A
lantibiotics are elongated, amphiphilic
peptides, while type-B
lantibiotics are compact and globular. In the last decade there has been a marked increase in research interest in these
peptides due both to the novel biosynthetic mechanisms by which they are produced, as well as to their potential applications.
Lantibiotics are synthesised on the ribosome as a prepeptide which undergoes several post-translational modification events, including
dehydration of specific
hydroxyl amino acids to form dehydroamino
acids, addition of neighbouring sulfhydryl groups to form
thioethers and, in specific cases, other modifications such as introduction of D-
alanine residues from
L-serine, formation of
lysinoalanine bridges, formation of novel N-terminal blocking groups and oxidative decarboxylation of a C-terminal
cysteine. The genetic elements responsible for these specific modification reactions encode unique
enzymes with hitherto unknown reaction mechanisms. Production of these
peptides also requires accessory
proteins including processing
proteases, translocators of the
ATP-binding cassette transporter family, regulatory
proteins and dedicated producer self-protection mechanisms. While the principle
biological activity of most type-B
lantibiotics appears to be directed at the inhibition of
enzyme functions, the type-A
lantibiotics kill bacterial cells by forming pores in the cytoplasmic membrane.