Crystal structure of the neurophysin-oxytocin complex

Area of Science:

• Biochemistry
• Structural Biology
• Endocrinology

Background:

• Oxytocin is a crucial pituitary hormone involved in social bonding and reproduction.
• Neurophysin serves as a carrier protein for oxytocin, facilitating its transport and release.
• Understanding the structural basis of neurophysin-oxytocin interaction is vital for comprehending hormone function.

Purpose of the Study:

• To determine the high-resolution crystal structure of the oxytocin-neurophysin complex.
• To identify key residues involved in the recognition and binding of oxytocin by neurophysin.
• To compare the structural insights from X-ray crystallography with previous NMR-derived models.

Main Methods:

• X-ray crystallography was employed to determine the structure of the neurophysin-oxytocin complex.
• The crystal structure was refined to a resolution of 3.0 Angstroms.
• Comparative analysis was performed with existing X-ray structures of oxytocin analogues and NMR data.

Main Results:

• The first crystal structure of the pituitary hormone oxytocin complexed with its carrier protein neurophysin was determined.
• The hormone-binding site is located at the terminus of a 3(10)-helix, involving residues from both neurophysin domains.
• Key residues Tyr 2 and Cys 1 of oxytocin were confirmed as critical for neurophysin recognition, with Tyr 2 deeply buried.

Conclusions:

• The crystal structure provides detailed insights into the molecular interactions between oxytocin and neurophysin.
• The findings confirm the roles of specific oxytocin residues in binding.
• A discrepancy was noted between the crystallographic structure and NMR data regarding the recognition of Tyr 2 by neurophysin.