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| The EMBO Journal
(2000) 19, 3649–3656, doi:10.1093/emboj/19.14.3649 |
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| On the binding mechanism of the peptide receptor of the oligopeptide transport system of Lactococcus lactis |
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| Frank C. Lanfermeijer1, 2, Frank J.M. Detmers1, Wil N. Konings1 and Bert Poolman1, 3 |
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1 Departments of Microbiology and Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, The Netherlands 2 Present address: Department of Molecular Biology of Plants, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands 3 Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands To whom correspondence should be addressed Bert Poolman, b.poolman@chem.rug.nl Received 4 May 2000; Revised 1 June 2000; Accepted 1 June 2000. |
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| Abstract |
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Lactococcus lactis degrades exogenous proteins such as  -casein to peptides of 4–30 amino acids, and uses these as nitrogen sources. The binding protein or receptor (OppALl) of the oligopeptide transport system (Opp) of L.lactis has the unique capacity to bind peptides from five up to at least 20 residues. To study the binding mechanism of OppALl, nonameric peptides were used in which the cysteine at position 1, 3, 4, 5, 6, 7 or 9 was selectively labeled with either bulky and non-fluorescent or bulky and fluorescent groups. Also, nonameric peptides with a non-natural residue, azatryptophan, at positions 3 or 7 were used. The fluorescence of azatryptophan reports on the polarity of the environment. The studies indicate that the binding protein encloses the first six amino acids of the peptide, whereas the remaining residues stick out and interact with the surface of the binding protein. The peptide binding mechanism of OppALl is discussed in relation to known three-dimensional structures of members of this class of proteins, and an adaptation of the general binding mechanism is proposed. |
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| Keywords: ABC transporter, binding mechanism, binding protein-dependent transport, oligopeptide |
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