Dynamic structure of metallothionein.

Area of Science:

• Biochemistry
• Protein Chemistry
• Biophysical Chemistry

Background:

• Metallothioneins (MTs) are cysteine-rich proteins involved in metal detoxification and homeostasis.
• The structural and dynamic properties of MTs are crucial for their biological functions.
• Understanding MT conformational changes is key to elucidating their interaction mechanisms.

Purpose of the Study:

• To investigate the effect of ionic strength on the molecular conformation and hydrodynamic properties of rabbit liver metallothionein.
• To explore the relationship between protein structure, charge, and environmental conditions.
• To identify potential conformational states of metallothionein.

Main Methods:

• Molecular sieve chromatography was employed to assess changes in Stokes radius at varying electrolyte concentrations.
• Far-UV circular dichroism spectroscopy was utilized to detect alterations in protein secondary structure.
• Analysis focused on the influence of ionic strength on protein conformation.

Main Results:

• A significant increase in the Stokes radius of rabbit liver metallothionein was observed as ionic strength decreased from 0.5 to 0.015.
• Far-UV circular dichroism spectra indicated a conformational transition in metallothionein with changing ionic strength.
• These changes are attributed to electrostatic repulsions between negatively charged metal-thiolate clusters.

Conclusions:

• Metallothionein exhibits altered molecular shape and/or hydration in response to variations in ionic strength.
• The protein likely exists in at least two interchangeable conformational states.
• The equilibrium between these states is governed by the electrostatic free energy of the system.