Three-dimensional structure of the two peptides that constitute the two-peptide bacteriocin lactococcin G.
The three-dimensional structures of the two peptides, lactococcin G-alpha (LcnG-alpha; contains 39 residues) and lactococcin G-beta (LcnG-beta, contains 35 residues), that constitute the two-peptide bacteriocin lactococcin G (LcnG) have been determined by nuclear magnetic resonance (NMR) spectroscopy in the presence of DPC micelles and TFE. In DPC, LcnG-alpha has an N-terminal alpha-helix (residues 3-21) that contains a GxxxG helix-helix interaction motif (residues 7-11) and a less well defined C-terminal alpha-helix (residues 24-34), and in between (residues 18-22) there is a second somewhat flexible GxxxG-motif. Its structure in TFE was similar. In DPC, LcnG-beta has an N-terminal alpha-helix (residues 6-19). The region from residues 20 to 35, which also contains a flexible GxxxG-motif (residues 18-22), appeared to be fairly unstructured in DPC. In the presence of TFE, however, the region between and including residues 23 and 32 formed a well defined alpha-helix. The N-terminal helix between and including residues 6 and 19 seen in the presence of DPC, was broken at residues 8 and 9 in the presence of TFE. The N-terminal helices, both in LcnG-alpha and -beta, are amphiphilic. We postulate that LcnG-alpha and -beta have a parallel orientation and interact through helix-helix interactions involving the first GxxxG (residues 7-11) motif in LcnG-alpha and the one (residues 18-22) in LcnG-beta, and that they thus lie in a staggered fashion relative to each other.
Rogne
Per
P
Department of Molecular Biosciences, University of Oslo, Pb 1041 Blindern, 0316 Oslo, Norway.
Fimland
Gunnar
G
Nissen-Meyer
Jon
J
Kristiansen
Per Eugen
PE
D000595:Amino Acid Sequence; D001430:Bacteriocins / Q000737:chemistry* / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides / Q000737:chemistry* / Q000235:genetics; D011487:Protein Conformation
D001430:Bacteriocins; C095766:LagA protein, Lactococcus lactis; D010455:Peptides; C110915:lactococcin G