Kinetic and molecular dynamics studies on the metal‐dependent folding of metallothionein (MT)

• Published in: The FASEB journal 2006-03, Vol.20 (4), p.A501-A501
• Main Authors: Duncan, Kelly E Rigby, Stillman, Martin J
• Format: Article
• Language: English
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fasebj.20.4.A501-a

Metal‐induced chelation is the driving force for the folding of the α and β domains of MT, however, the exact mechanism is unknown. Elucidation of this mechanistic process extends beyond MT to encompass other metalloproteins that rely on metal coordination to achieve a properly folded conformation. In this study, kinetic measurements were made of the metallation reaction to the individual domains of MT using stopped‐flow (SF) spectroscopy. Metal coordination was monitored by UV absorption at 250 nm corresponding to the ligand‐to‐metal charge transfer of the cysteinyl sulfur to the Cd2+ ion. The metallation reaction was complete within the 2 ms dead time of the instrument at low temperature (8 °C) and low concentration (1.25 μM). This fast rate of reaction was confirmed using SF‐circular dichroism spectroscopy on the α fragment of MT. Molecular modeling was used to investigate the behavior of the protein backbone upon demetallation and to search for stable peptide conformations in the metal‐free state. The molecular dynamics (MM3) calculations showed an increase in the number of H‐bonds upon sequential demetallation suggesting possible structural stabilization via a H‐bonding network. In addition, the MD calculations showed movement of the Cys side chains from the inside of the domain core when in the metallated state to the outside surface upon metal removal. Financial support provided by NSERC (equipment/operating to MJS and Post‐Graduate Scholarships A & D to KERD) and ADF at UWO.