Structure of a rhombohedral R6 insulin/phenol complex

Area of Science:

• Biochemistry and structural biology
• Protein crystallography

Background:

• Hexameric insulin exhibits various crystalline forms depending on crystallization conditions.
• Understanding insulin's structure is crucial for diabetes treatment and drug development.

Purpose of the Study:

• To characterize a newly identified rhombohedral crystalline form of hexameric insulin.
• To elucidate the structural details and conformational properties of this insulin crystal.

Main Methods:

• Crystallization of hexameric insulin under specific conditions (1% phenol, pH 8.5).
• X-ray diffraction analysis to determine the crystal structure.
• Structure refinement using diffraction data to 2.5A resolution.

Main Results:

• A new rhombohedral crystal form (space group R3) was obtained.
• The asymmetric unit contains a dimer with monomers in similar R conformations.
• Alpha-helical structures were observed from residues B1-B19.
• Phenol molecules are involved in hydrogen bonding and coordination with zinc ions.

Conclusions:

• The study presents a novel rhombohedral crystal structure of hexameric insulin.
• Detailed structural analysis reveals specific monomer conformations and interactions with phenol and zinc.
• This structural information contributes to the understanding of insulin's molecular organization.