Photo-chemically induced dynamic nuclear polarization (CIDNP)-NMR spectroscopy at 360 MHz has been used to investigate pH-induced conformational transitions in mouse epidermal growth factor. At about pH 9, all five tyrosine residues and both tryptophan residues are, to various extents, solvent-exposed, while the His-22 residue is buried in the protein matrix. Tyr-13 is the least exposed of the tyrosine residues and also the most immobilized. As the pH is decreased to 5.9, the tryptophan residues gradually become less exposed, while the Tyr-13 residue becomes internalized in the protein. These data suggest that the C-terminus and part of the N-terminal structural domain are affected by a conformational transition in mouse epidermal growth factor occurring between pH 6 and 8 via breakage of the His-22 inter-residue linkage. Above pH 9, a decreased photo-CIDNP effect is evident for both tryptophans and for Tyr-10 and Tyr-13; this information suggests that a second conformational change takes place at basic pH, which may simply be incipient denaturation.
|Original language||English (US)|
|Number of pages||6|
|Journal||Biochimica et Biophysica Acta (BBA)/Protein Structure and Molecular|
|State||Published - Nov 21 1986|
Bibliographical noteFunding Information:
This work was supported by a grant from the National Institutes of Health (U.S.A.) (GM-34662) (to K.H.M) and from a generous gift from the Glenmede Trust Fund to Temple University and benefitted from NMR facilities made available to Yale University through grant CHE-7916210 from the National Science Foundation. This work was also supported by a grant from the North Atlantic Treaty Organization (NATO) Scientific Affairs Division (RG.85/0424) (to K.H.M. and A.D.).
- Conformational change
- Epidermal growth factor
- H-NMR spectroscopy
- two-dimensional NMR