CRYSTAL-STRUCTURE OF THE NEUROPHYSIN-OXYTOCIN COMPLEX

The first crystal structure of the pituitary hormone oxytocin complexe d with its carrier protein neurophysin has been determined and refined to 3.0 Angstrom resolution. The hormone-binding site is located at th e end of a 3(10)-helix and involves residues from both domains of each monomer. Hormone residues Tyr 2, which is buried deep in the binding pocket, and Cys 1 have been confirmed as the key residues involved in neurophysin-hormone recognition. We have compared the bound oxytocin o bserved in the neurophysin-oxytocin complex, the X-ray structures of u nbound oxytocin analogues and the NMR-derived structure for bound oxyt ocin. We find that while our structure is in agreement with the previo us crystallographic findings, it differs from the NMR result with rega rd to how Tyr 2 of the hormone is recognized by neurophysin.