The structure of pyogenecin immunity protein, a novel bacteriocin-like immunity protein from Streptococcus pyogenes
1 Midwest Center for Structural Genomics and Structural Biology Center, Biosciences Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
2 Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, CB10 1SA, UK
3 Midwest Center for Structural Genomics, Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22903, USA
4 Midwest Center for Structural Genomics, Department of Biochemistry, UT Southwestern Medical Center at Dallas, Dallas, TX 75235, USA
BMC Structural Biology 2009, 9:75 doi:10.1186/1472-6807-9-75Published: 17 December 2009
Many Gram-positive lactic acid bacteria (LAB) produce anti-bacterial peptides and small proteins called bacteriocins, which enable them to compete against other bacteria in the environment. These peptides fall structurally into three different classes, I, II, III, with class IIa being pediocin-like single entities and class IIb being two-peptide bacteriocins. Self-protective cognate immunity proteins are usually co-transcribed with these toxins. Several examples of cognates for IIa have already been solved structurally. Streptococcus pyogenes, closely related to LAB, is one of the most common human pathogens, so knowledge of how it competes against other LAB species is likely to prove invaluable.
We have solved the crystal structure of the gene-product of locus Spy_2152 from S. pyogenes, (PDB:2fu2), and found it to comprise an anti-parallel four-helix bundle that is structurally similar to other bacteriocin immunity proteins. Sequence analyses indicate this protein to be a possible immunity protein protective against class IIa or IIb bacteriocins. However, given that S. pyogenes appears to lack any IIa pediocin-like proteins but does possess class IIb bacteriocins, we suggest this protein confers immunity to IIb-like peptides.
Combined structural, genomic and proteomic analyses have allowed the identification and in silico characterization of a new putative immunity protein from S. pyogenes, possibly the first structure of an immunity protein protective against potential class IIb two-peptide bacteriocins. We have named the two pairs of putative bacteriocins found in S. pyogenes pyogenecin 1, 2, 3 and 4.