Epidermal growth factor from the mouse. Physical evidence for a tiered .beta.-sheet domain: two-dimensional NMR correlated spectroscopy and nuclear overhauser experiments on backbone amide protons

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Abstract
When H2O-exchanged, lyophilized mouse epidermal growth factor (mEGF) is dissolved in deuterium oxide at low pH (i.e., below .apprx. 6.0), 13 well-resolved, amide proton resonances are observed in the downfield region of an NMR spectrum (500 MHz). Under the conditions of these experiments, the lifetimes of these amide protons in exchange for deuterons of the deuterium oxide solvent suggest that these amide protons are H-bonded, backbone amide protons. Several of these amide proton resonances show splittings (i.e., JNH.alpha.-CH) of .apprx. 8-10 Hz, indicating that their associated amide protons are in some type of .beta.-structure. Selective nuclear Overhauser effect (NOE) experiments performed on all amide proton resonances strongly suggest that all 13 of these backbone amide protons are part of a single-tiered .beta.-sheet structural domain in mEGF. Correlation of 2D NMR correlated spectroscopy data, identifying scaler coupled protons, with NOE data, identifying protons close to the irradiated amide protons, allows tentative assignment of some resonances in the NOE difference spectra to specific amino acid residues. These data allow a partial structural model of the tiered .beta.-sheet domain in mEGF to be postulated.

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