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Epidermal growth factor: exposure and dynamics of the aromatic side chains as investigated by photo‐CIDNP and variable temperature 1 H‐NMR
Author(s) -
De Marco Antonio,
Menegatti Enea,
Guarneri Mario
Publication year - 1983
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(83)80446-3
Subject(s) - chemistry , cidnp , side chain , homonuclear molecule , globular protein , crystallography , stereochemistry , molecule , organic chemistry , polymer , polarization (electrochemistry)
EGF is a 53 residue polypeptide of multiple biological activities. Homonuclear decoupling, spin‐echo multiplet selection and Photo‐CIDNP experiments lead us to fully assign the resonances from the aromatic side chains (5 Tyr, 1 His and 2 Trp). The photochemical experiment gives specific attribution of doublets in tyrosines and multiplets in tryptophans. The resonances from two tyrosines are broadened and shifted at high fields, suggesting the existence of hydrophobic domains in EGF, consistent with the presence of ring current shifted methyl resonances. However, the amide exchange in D 2 O solution is considerably faster than that observed for globular proteins of the same size, and most of the aromatic residues are accessible to the flavin dye. The combined evidence suggests that EGF possesses a folded structure, but the molecule is rather floppy. From spectra measured at variable temperature a Δ G ° at 25°C of about 8 kcal/mol is calculated.