Binding of a dimeric derivative of vancomycin to L-Lys-D-Ala-D-lactate in solution and at a surface.
BACKGROUND
The emergence of bacteria that are resistant to vancomycin (V), a glycopeptide antibiotic, results from the replacement of the carboxy-terminal D-Ala-D-Ala of bacterial cell wall precursors by D-Ala-D-lactate. Recently, it has been demonstrated that covalent dimeric variants of V are active against vancomycin-resistant enterococci (VRE). To study the contribution of divalency to the activities of these variants, we modeled the interactions of V and a dimeric V with L-Lys-D-Ala-D-lactate, an analog of the cell-wall precursors of the vancomycin-resistant bacteria.


RESULTS
A dimeric derivative of V (V-Rd-V) was found to be much more effective than V in inhibiting the growth of VRE. The interactions of V and V-Rd-V with a monomeric lactate ligand - diacetyl-L-Lys-D-Ala-D-lactate (Ac2KDADLac) - and a dimeric derivative of L-Lys-D-Ala-D-lactate (Lac-R'd-Lac) in solution have been examined using isothermal titration calorimetry and UV spectroscopy titrations; the results reveal that V-Rd-V binds Lac-R'd-Lac approximately 40 times more tightly than V binds Ac2KDADLac. Binding of V and of V-Rd-V to Nalpha-Ac-L-Lys-D-Ala-D-lactate presented on the surface of mixed self-assembled monolayers (SAMs) of alkanethiolates on gold indicates that the apparent off-rate for dissociation of V-Rd-V from the surface is much slower than that of V from the same surface.


CONCLUSIONS
The results are compatible with the hypothesis that divalency is responsible for tight binding, which correlates with small values of minimum inhibitory concentrations of V and V-Rd-V.
Rao
J
J
Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA.
Yan
L
L
Lahiri
J
J
Whitesides
G M
GM
Weis
R M
RM
Warren
H S
HS
D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000378:metabolism; D001419:Bacteria / Q000187:drug effects / Q000378:metabolism; D001665:Binding Sites; D002473:Cell Wall / Q000378:metabolism; D019281:Dimerization; D004151:Dipeptides / Q000378:metabolism*; D004352:Drug Resistance, Microbial; D007700:Kinetics; D007773:Lactates / Q000378:metabolism*; D008954:Models, Biological; D012996:Solutions; D020349:Surface Plasmon Resonance; D013499:Surface Properties; D014640:Vancomycin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism
D000900:Anti-Bacterial Agents; D004151:Dipeptides; D007773:Lactates; D012996:Solutions; C120521:lysyl-alanyl-lactate; D014640:Vancomycin