title: Close pairs of carboxylates: a possibility of multicenter hydrogen bonds in proteins.
abstract: Covalent attachment of hydrogen to the donor atom may be not an essential characteristic of stable hydrogen bonds. A positively charged particle (such as a proton), located between the two negatively charged residues, may lead to a stable interaction of the two negative residues. This paper analyzes close Asp-Glu pairs of residues in a large set of protein chains; 840 such pairs of residues were identified, of which 28% were stabilized by a metal ion, 12% by a positive residue nearby and 60% are likely to be stabilized by a proton. The absence of apparent structural constraints, secondary structure preferences, somewhat lower B-factors and a distinct correlation between pH and the minimal O-O distance in carboxylate pairs suggest that most of the abnormally close pairs could indeed be stabilized by a shared proton. Implications for protein stability and modeling are discussed.
authors.affiliation: Biology Department, Georgia State University, Atlanta, GA 30303, USA. biotiy@suez.cs.gsu.edu
authors.forename: Ivan Y
authors.initials: IY
authors.lastname: Torshin
authors.forename: Robert W
authors.initials: RW
authors.lastname: Harrison
authors.forename: Irene T
authors.initials: IT
authors.lastname: Weber
mesh_terms: D024342:Amino Acids, Acidic / Q000378:metabolism*; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D011487:Protein Conformation; D011506:Proteins / Q000378:metabolism*; D055672:Static Electricity
chemical_list: D024342:Amino Acids, Acidic; D011506:Proteins