Molecular mechanisms of ion-specific effects on proteins.
The specific binding sites of Hofmeister ions with an uncharged 600-residue elastin-like polypeptide, (VPGVG)(120), were elucidated using a combination of NMR and thermodynamic measurements along with molecular dynamics simulations. It was found that the large soft anions such as SCN(-) and I(-) interact with the polypeptide backbone via a hybrid binding site that consists of the amide nitrogen and the adjacent α-carbon. The hydrocarbon groups at these sites bear a slight positive charge, which enhances anion binding without disrupting specific hydrogen bonds to water molecules. The hydrophobic side chains do not contribute significantly to anion binding or the corresponding salting-in behavior of the biopolymer. Cl(-) binds far more weakly to the amide nitrogen/α-carbon binding site, while SO(4)(2-) is repelled from both the backbone and hydrophobic side chains of the polypeptide. The Na(+) counterions are also repelled from the polypeptide. The identification of these molecular-level binding sites provides new insights into the mechanism of peptide-anion interactions.
Department of Chemistry, Texas A&M University, College Station, Texas 77843, USA.
Kelvin B
KB
Rembert
Jana
J
Paterová
Jan
J
Heyda
Christian
C
Hilty
Pavel
P
Jungwirth
Paul S
PS
Cremer
D000595:Amino Acid Sequence; D000838:Anions / Q000737:chemistry; D001665:Binding Sites; D006860:Hydrogen Bonding; D007477:Ions / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides / Q000737:chemistry*; D013816:Thermodynamics
D000838:Anions; D007477:Ions; D010455:Peptides; C033943:elastin polypentapeptide