Bacteriocin AS-48, a microbial cyclic polypeptide structurally and functionally related to mammalian NK-lysin.
The solution structure of bacteriocin AS-48, a 70-residue cyclic polypeptide from Enterococcus faecalis, consists of a globular arrangement of five alpha-helices enclosing a compact hydrophobic core. The head-to-tail union lies in the middle of helix 5, a fact that is shown to have a pronounced effect on the stability of the three-dimensional structure. Positive charges in the side chains of residues in helix 4 and in the turn linking helix 4 to helix 5 form a cluster that most probably determine its antibacterial activity by promoting pore formation in cell membranes. A similar five-helix structural motif has been found in the antimicrobial NK-lysin, an effector polypeptide of T and natural killer (NK) cells. Bacteriocin AS-48 lacks the three disulfide bridges characteristic of the saposin fold present in NK-lysin, and has no sequence homology with it. Nevertheless, the similar molecular architecture and high positive charge strongly suggest a common mechanism of antibacterial action.
González
C
C
Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Cientificas, Madrid 28006, Spain.
Langdon
G M
GM
Bruix
M
M
Gálvez
A
A
Valdivia
E
E
Maqueda
M
M
Rico
M
M
D001426:Bacterial Proteins / Q000737:chemistry*; D001430:Bacteriocins / Q000737:chemistry*; D013293:Enterococcus faecalis / Q000737:chemistry*; D008958:Models, Molecular; D011487:Protein Conformation; D011510:Proteolipids / Q000737:chemistry*; D011663:Pulmonary Surfactants / Q000737:chemistry*; D055672:Static Electricity
D001426:Bacterial Proteins; D001430:Bacteriocins; C093238:NK-lysin; D011510:Proteolipids; D011663:Pulmonary Surfactants; C065279:bacteriocin Bc 48