The class IId bacteriocin lactococcin A and the pediocin-like bacteriocins induce membrane leakage and cell death by specifically binding the mannose phophotransferase system (man-PTS) on their target cells. The bacteriocins' cognate immunity proteins that protect the producer cell from its own bacteriocin recognize and bind to the bacteriocin-man-PTS complex and thereby block membrane leakage. In this study, we have determined the three-dimensional structure of the lactococcin A immunity protein (LciA) by the use of nuclear magnetic resonance spectroscopy. LciA forms a four-helix bundle structure with a flexible C-terminal tail. Despite the low degree of sequence similarity between LciA and the pediocin-like immunity proteins, they share the same fold. However, there are certain differences between the structures. The C-terminal helix in LciA is considerably shorter than that observed in the pediocin-like immunity proteins, and the surface potentials of the immunity proteins differ. Truncated variants of LciA in which 6 or 10 of the C-terminal residues were removed yielded a reduced degree of protection, indicating that the unstructured C-terminal tail is important for the functionality of the immunity proteins.

Nuclear Magnetic Resonance Structure and Mutational Analysis of the Lactococcin A Immunity Protein

Virginia Fuochi;
2016

Abstract

The class IId bacteriocin lactococcin A and the pediocin-like bacteriocins induce membrane leakage and cell death by specifically binding the mannose phophotransferase system (man-PTS) on their target cells. The bacteriocins' cognate immunity proteins that protect the producer cell from its own bacteriocin recognize and bind to the bacteriocin-man-PTS complex and thereby block membrane leakage. In this study, we have determined the three-dimensional structure of the lactococcin A immunity protein (LciA) by the use of nuclear magnetic resonance spectroscopy. LciA forms a four-helix bundle structure with a flexible C-terminal tail. Despite the low degree of sequence similarity between LciA and the pediocin-like immunity proteins, they share the same fold. However, there are certain differences between the structures. The C-terminal helix in LciA is considerably shorter than that observed in the pediocin-like immunity proteins, and the surface potentials of the immunity proteins differ. Truncated variants of LciA in which 6 or 10 of the C-terminal residues were removed yielded a reduced degree of protection, indicating that the unstructured C-terminal tail is important for the functionality of the immunity proteins.
Bacteriocins; DNA Mutational Analysis; Lactococcus lactis; Magnetic Resonance Spectroscopy; Models, Molecular; Mutation; Phosphoenolpyruvate Sugar Phosphotransferase System; Protein Binding; Protein Domains; Protein Structure, Secondary; Biochemistry
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/20.500.11769/355412
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