Oxford University Press, FEMS Microbiology Letters, 1(227), p. 33-38, 2003
DOI: 10.1016/s0378-1097(03)00662-1
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The genome sequence of Lactococcus lactis IL1403 revealed the presence of a putative peptide-binding protein-dependent ABC-transporter (Dpp). The genes for two peptide-binding proteins (dppA and dppP) precede the membrane components, which include two transmembrane protein genes (dppB and dppC) and two ATP-binding protein genes (dppD and dppF). In this work, the gene specifying the second peptide-binding protein (DppP) was cloned under the control of the nisin promoter. The protein fused to a carboxyl-terminal histidine tag (DppP-His(6)) was purified and its binding properties were determined by monitoring the intrinsic fluorescence changes observed upon ligand binding. The major features of peptide binding to DppP-His(6) include: (i) a requirement for a free N-terminal alpha-amino group in the ligand; (ii) a high affinity for di-, tri- and tetra-peptides; (iii) affinity constants for peptide binding independent of pH; and (iv) a high affinity for D-isomer-containing peptides. Remarkably, the features (ii), (iii) and (iv) differ from those previously reported for DppA-His(6), suggesting that DppP-His(6) is a more versatile peptide-binding protein that could have additional functions.