Insight into the cation-π interaction at the metal binding site of the copper metallochaperone CusF.
The periplasmic Cu(+)/Ag(+) chaperone CusF features a novel cation-π interaction between a Cu(+)/Ag(+) ion and Trp44 at the metal binding site. The nature and strength of the Cu(+)/Ag(+)-Trp44 interactions were investigated using computational methodologies. Quantum-mechanical (QM) calculations showed that the Cu(+) and Ag(+) interactions with Trp44 are of similar strength (~14 kcal/mol) and bond order. Quantum-mechanical/molecular-mechanical (QM/MM) calculations showed that Cu(+) binds in a distorted tetrahedral coordination environment in the Trp44Met mutant, which lacks the cation-π interaction. Molecular dynamics (MD) simulations of CusF in the apo and Cu(+)-bound states emphasized the importance of the Cu(+)-Trp44 interaction in protecting Cu(+) from water oxidation. The protein structure does not change over the time scale of hundreds of nanoseconds in the metal-bound state. The metal recognition site exhibits small motions in the apo state but remains largely preorganized toward metal binding. Trp44 remains oriented to form the cation-π interaction in the apo state and faces an energetic penalty to move away from the metal ion. Cu(+) binding quenches the protein's internal motions in regions linked to binding CusB, suggesting that protein motions play an essential role in Cu(+) transfer to CusB.
Department of Chemistry and Quantum Theory Project, University of Florida, 2238 New Physics Building, P.O. Box 118435, Gainesville, Florida 32611-8435, USA.
Dhruva K
DK
Chakravorty
Bing
B
Wang
Melek N
MN
Ucisik
Kenneth M
KM
Merz
D001665:Binding Sites; D027682:Cation Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003300:Copper / Q000378:metabolism*; D000079922:Copper Transport Proteins; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D056511:Metallochaperones / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D056004:Molecular Dynamics Simulation; D009154:Mutation; D012834:Silver / Q000378:metabolism
D027682:Cation Transport Proteins; D000079922:Copper Transport Proteins; C506213:CusF protein, E coli; D029968:Escherichia coli Proteins; D056511:Metallochaperones; D012834:Silver; D003300:Copper