Carbon-13 nuclear magnetic resonance studies of the interaction of specifically labeled (90%-13C) oxytocin and arginine vasopressin with neurophysins

Organic chemistry and biology: chemical biology through the eyes of collaboration

From a scientific perspective, efforts to understand biology including what constitutes health and disease has become a chemical problem. However, chemists and biologists "see" the problems of understanding biology from different perspectives, and this has retarded progress in solving the problems especially as they relate to health and disease. This suggests that close collaboration between chemists and biologists is not only necessary but essential for progress in both the biology and chemistry that will provide solutions to the global questions of biology. This perspective has directed my scientific efforts for the past 45 years, and in this overview I provide my perspective of how the applications of synthetic chemistry, structural design, and numerous other chemical principles have intersected in my collaborations with biologists to provide new tools, new science, and new insights that were only made possible and fruitful by these collaborations.

Transfer nuclear Overhauser effect study of the conformation of oxytocin bound to bovine neurophysin I

This study reports the structure of the peptide hormone oxytocin bound to its carrier protein, neurophysin I, obtained by nuclear magnetic resonance techniques. At the pH value of 2.1 in our experiments, the ligand is in fast exchange with its carrier protein, allowing the use of transfer-NOE methods. The number of distance constraints for the peptide being limited, considerable attention has been paid to an accurate distance determination. The resulting accurate distance limits were used as input for a distance geometry calculation followed by a restrained molecular dynamics run. Convergence to a well-defined family of structures for oxytocin in its bound state was reached. Both the backbone and the side-chain conformations differ between the bound form and the crystal structure of free oxytocin [Wood, S. P., et al. (1986) Science 232, 633]. These differences, as well as other structural features of the bound form, are discussed in terms of interactions made with the carrier protein. Transfer-NOE experiments at low peptide protein ratios provide direct experimental evidence for contacts between the oxytocin Tyr2 residue and an aromatic residue of neurophysin. The resonance assignments of the aromatic groups [Whittaker, B. A., et al. (1985) Biochemistry 24, 2782] together with the recently published X-ray structure of the neurophysin II protein complexed with a dipeptide [Chen et al. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 4240] allow us to assign the aromatic signal on the protein to the neurophysin Phe22 residue.