Comparison of the dynamics of an engineered insulin monomer and dimer by acid-quenched amide proton exchange. Non-local stabilization of interchain hydrogen bonds by dimerization.
Dynamic differences between an engineered insulin monomer and dimer are investigated under physiological conditions by an adaptation of the method of acid-quenched amide proton exchange. Although exchange lifetimes of amide protons involved in intrachain hydrogen bonds are similar in the two analogs, dimerization specifically stabilizes two interchain hydrogen bonds (LeuB6-NH...O = C-CysA6 and CysA11-NH...O = C-GluB4) that are distant from the dimer interface. Such non-local stabilization demonstrates that fluctuations in the tertiary structure of the monomer are damped by dimerization. As the B6-A6 and A11-B4 hydrogen bonds are specific to the crystallographic T-state, their stabilization also indicates that the R-state (an allosteric feature of hexamer assembly) is not significantly populated in an isolated dimer. Our results are discussed in reference to recent hypotheses that crystal structures of insulin depict inactive conformers and that detachment of interchain contacts accompany receptor binding.
Hua
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QX
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115.
Jia
W
W
Frank
B H
BH
Weiss
M A
MA
D000577:Amides; D000595:Amino Acid Sequence; D004355:Drug Stability; D006860:Hydrogen Bonding; D007328:Insulin / Q000031:analogs & derivatives* / Q000737:chemistry*; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008961:Models, Structural; D008969:Molecular Sequence Data; D015202:Protein Engineering; D017433:Protein Structure, Secondary; D014961:X-Ray Diffraction / Q000379:methods
D000577:Amides; D007328:Insulin; D046911:Macromolecular Substances