Metal binding to yeast aminopeptidase I

Area of Science:

• Biochemistry
• Enzymology
• Protein-metal interactions

Background:

• Yeast aminopeptidase I is a dodecameric enzyme.
• Understanding metal ion binding is crucial for enzyme function.

Purpose of the Study:

• To investigate the binding of Zn(II) and Co(II) to yeast aminopeptidase I.
• To elucidate the mechanism of metal binding and enzyme reconstitution.

Main Methods:

• Enzyme activity assays with varying metal concentrations.
• Metal buffer systems to control metal ion levels.
• Equilibrium binding studies and chemical modification.

Main Results:

• Sigmoidal binding curves with Hill coefficients of 1.2-1.6.
• Substoichiometric metal binding (0.5-0.6 mol metal/mol subunit).
• Evidence suggests histidine residues are involved in metal coordination.
• Reconstitution and inactivation are slow processes (minute range).

Conclusions:

• Yeast aminopeptidase I exhibits complex metal binding kinetics.
• A proposed model involves a slow conformational transition for reconstitution.
• Histidine residues play a key role in Zn(II) and Co(II) binding.