Structural and dynamical comparison of alpha, beta and gamma forms of murine epidermal growth factor

Two-, three-, and four-dimensional nuclear magnetic resonance spectroscopy of protein pharmaceuticals

Advances in NMR spectroscopy and related computational methods continue at a rapid pace. In the past three years, the capability to make complete assignments of protein spectra has expanded from a limit of approximately 100 residues to a limit of possibly 400 residues via isotope-edited three- and four-dimensional methods.

Synthesis of a cyclic analogue of the C-loop region of epidermal growth factor, containing 1-aminocyclopropane-1-carboxylic acid

We report the synthesis of a cyclic analogue of epidermal growth factor sequence 33-42 with substitution of 1-aminocyclopropane-1-carboxylic acid for glycine at position 39 (N-acetyl-Cys-Val-Ile-Gly-Tyr-Ser-ACPCA-Asp-Arg-Cys-NH2). The analogue was synthesised by solid-phase methods, using t-Boc chemistry and acid-labile side-chain protecting groups. The use of the 4-methoxybenzyl protecting group for C- and N-terminal cysteine residues resulted in the spontaneous formation of the desired intramolecular disulfide bond after HF deprotection.

pH sensitivity of epidermal growth factor receptor complexes

The association/dissociation binding kinetics of 125I-labeled mouse epidermal growth factor (EGF) to receptors on human fibroblast cells in monolayer culture have been measured at 4 degrees C as a function of extracellular pH from pH 5-9. At pH 8, steady-state total binding is maximal. As pH is lowered to 6.5, total binding monotonically decreases dramatically. It changes further only slightly between pH 6.5 and 5 to about 20% of the maximum binding value. Scatchard binding plots at pH 7.5 and above show the commonly observed concave-upward, non-linear curve; as pH is lowered, this plot becomes much more linear, indicating that the "high affinity" bound receptor population is greatly diminished. Application of our ternary complex binding model [Mayo et al., J Biol Chem 264:17838-17844, 1989], which hypothesizes complexation of the EGF-bound receptor with a cell surface interaction molecule, indicates that pH may have some direct effects on ternary complex formation, but the major effect is on EGF-receptor dissociation.

Sequence-specific 1H-n.m.r. assignments and peptide backbone conformation in rat epidermal growth factor

The solution conformation of rat epidermal growth factor (EGF) has been investigated by proton n.m.r. techniques. Two-dimensional proton n.m.r. experiments have allowed sequential resonance assignments to be made for most protons. On the basis of these assignments, two regions of anti-parallel beta-sheet structure have been derived from the n.m.r. data. A beta-sheet segment running from about V19 to V23 (capital letters refer to amino acids in the single-letter notation) is folded onto a beta-sheet segment running from R28 to N32 and joined by a chain reversal from E24 to D27. A second region involves a beta-turn from V34 to Y37, which starts a short beta-sheet up to G39, followed by a chain reversal up to Q43, which leads to folding of the C-terminal beta-sheet segment, i.e. H44-R45, running antiparallel to the short Y37 beta-sheet segment. The N-terminal segment up to G18 exists in a multiple bend conformation and is folded on to the V29-V23/R28-N32 beta-sheet such that Y10, Y13, Y22 and Y29 are proximal to each other. Structural comparison of rat, murine and human EGFs indicates a number of highly conserved structural features common to at least these species of EGF.