Observation of α-Helical Hydrogen-Bond Cooperativity in an Intact Protein

Abstract

The presence and extent of hydrogen bonding cooperativity in proteins remains a fundamental question, which in the past has been studied extensively, mostly by infrared and fluorescence measurements on model peptides. We demonstrate that such cooperativity can be studied in an intact protein by hydrogen/deuterium exchange NMR spectroscopy. The method is based on the fact that substitution of NH by ND in a backbone amide group slightly weakens the N-H…O=C hydrogen bond. Our results show that such substitution at position i in an α-helix impacts the 1H and 15N chemical shifts of the amide sites of residues i − 3 to i + 3. Quantum mechanical calculations indicate that the upfield shifts of 1H and 15N resonances at site i, observed upon H/D exchanges at sites i − 3, i + 1, i + 2, and i + 3, correspond to a decrease of the ith backbone amide electric dipole moment, which weakens its hydrogen bonding and long range electrostatic interactions with other backbone amides in the α-helix. These results provide new quantitative insights into the cooperativity of H-bonding in protein α-helices.

Polyol and sugar osmolytes can shorten protein hydrogen bonds to modulate function

“…2D 1 H- 15 N HSQC spectra were collected consecutively at 288 K. All the NMR spectra were processed and analyzed using NMRPipe and NMRDraw 62 . The exchange rates were obtained by fitting the 2D 1 H- 15 N HSQC peak height of each residue to a two-parameter (for H/D exchanges in buffer, sorbitol, and glucose) or three-parameter (for H/D exchanges in glycerol) exponential function 63 .…”

Strong Short‐Range Cooperativity in Hydrogen‐Bond Chains

“…Although many nanoscale and bulk properties may be influenced by the cooperativity of H‐bond networks, it is not possible to directly quantify interaction energies from structural or vibrational characteristics. In addition, discussion of the relative contributions of electrostatics, polarization, and covalency in H‐bond cooperativity5b, 9 is further exacerbated by the challenge of considering the influence of the surrounding solvent.…”

Evidences for Cooperative Resonance-Assisted Hydrogen Bonds in Protein Secondary Structure Analogs

“…A special property of these hydrogen bonds is their cooperativity, typified by the extra energy gain upon extension of the hydrogen bond units, (N−H···O = C) n . It was first reported by Salemme in 1982, and since then has been studied by many laboratories23456789. Several important protein behaviors, including the aggregation of β -amyloid peptides that may lead to Alzheimer’s disease or mad-cow disease, are attributed to this cooperativity10.…”