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PDBsum entry 1cw6
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Solution structure of carnobacteriocin b2 and implications for structure-Activity relationships among type iia bacteriocins from lactic acid bacteria.
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Authors
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Y.Wang,
M.E.Henz,
N.L.Gallagher,
S.Chai,
A.C.Gibbs,
L.Z.Yan,
M.E.Stiles,
D.S.Wishart,
J.C.Vederas.
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Ref.
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Biochemistry, 1999,
38,
15438-15447.
[DOI no: ]
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PubMed id
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Abstract
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Carnobacteriocin B2 (CbnB2), a type IIa bacteriocin, is a 48 residue
antimicrobial peptide from the lactic acid bacterium Carnobacterium pisicola
LV17B. Type IIa bacteriocins have a conserved YGNGVXC sequence near the
N-terminus and usually contain a disulfide bridge. CbnB2 seemed to be unique in
that its two cysteines (Cys9 and Cys14) could be isolated as free thiols [Quadri
et al. (1994) J. Biol. Chem. 26, 12204-12211]. To establish the structural
consequences of the presence or absence of a disulfide bridge and to investigate
if the YGNGVXC sequence is a receptor-binding motif [Fleury et al. (1996) J.
Biol. Chem. 271, 14421-14429], the three-dimensional solution structure of CbnB2
was determined by two-dimensional (1)H nuclear magnetic resonance (NMR)
techniques. Mass spectroscopic and thiol modification experiments on CbnB2 and
on model peptides, in conjunction with activity measurements, were used to
verify the redox status of CbnB2. The results show that CbnB2 readily forms a
disulfide bond and that this peptide has full antimicrobial activity. NMR
results indicate that CbnB2 in trifluoroethanol (TFE) has a well-defined central
helical structure (residues 18-39) but a disordered N terminus. Comparison of
the CbnB2 structure with the refined solution structure of leucocin A (LeuA),
another type IIa bacteriocin, indicates that the central helical structure is
conserved between the two peptides despite differences in sequence but that the
N-terminal structure (a proposed receptor binding site) is not. This is
unexpected because LeuA and CbnB2 exhibit >66% sequence identity in the first
24 residues. This suggests that the N-terminus, which had been proposed [Fleury
et al. (1996) J. Biol. Chem. 271, 14421-14429] to be a receptor binding site of
type IIa bacteriocins, may not be directly involved and that recognition of the
amphiphilic helical portion is the critical feature.
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