The structure of melittin. I. Structure determination and partial refinement

Area of Science:

• Biochemistry
• Structural Biology
• X-ray Crystallography

Background:

• Melittin, the main component of bee venom, possesses lytic properties.
• Despite its hydrophobic nature, melittin forms soluble tetramers in aqueous salt solutions.

Purpose of the Study:

• To determine the crystal structure of tetrameric melittin.
• To elucidate the structural basis of melittin's function and solubility.

Main Methods:

• X-ray crystallography at 2.8-A and 2.0-A resolution.
• Multiple isomorphous replacement technique.
• Partial atomic refinement and analysis of electron density maps.

Main Results:

• The crystal structure of tetrameric melittin was determined, revealing a structure with crystallographic and non-crystallographic 2-fold axes of symmetry.
• The melittin monomer exhibits two alpha-helical regions separated by a non-alpha-helical segment.
• Bound solvent molecules, likely crystallization ions, were identified interacting with the tetramer.

Conclusions:

• The determined structure provides insights into the quaternary structure of melittin.
• Understanding melittin's structure is key to comprehending its lytic mechanism and interactions.