The volume and compressibility changes of lysozyme associated with guanidinium chloride and pressure-assisted unfolding

The apparent specific volumes and isentropic compressibilities of hen egg white lysozyme were measured in aqueous guanidinium chloride solutions at 25 degrees C by means of a vibrational densimeter and a sing-around ultrasonic velocimeter. Little transition attributable to a protein unfolding was de...

Full description

Saved in:
Bibliographic Details
Published in:Journal of molecular biology 1999-08, Vol.291 (3), p.693-701
Main Authors: Sasahara, K, Sakurai, M, Nitta, K
Format: Article
Language:English
Subjects:
Animals
Chickens
Circular Dichroism
Female
Guanidine
Muramidase - chemistry
Pressure
Protein Denaturation
Protein Folding
Solutions
Spectrophotometry, Ultraviolet
Thermodynamics
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The apparent specific volumes and isentropic compressibilities of hen egg white lysozyme were measured in aqueous guanidinium chloride solutions at 25 degrees C by means of a vibrational densimeter and a sing-around ultrasonic velocimeter. Little transition attributable to a protein unfolding was detected in the partial specific volume, while the partial specific isentropic compressibility decreased slightly around the transition region. The pressure-assisted unfolding was also investigated in aqueous guanidinium chloride solutions by means of ultraviolet spectroscopy. Assuming a two-state transition model, it was found that the free energy change of unfolding depends almost linearly on pressure and the unfolding reaction is accompanied by a small decrease in volume. The compressibility behavior is in conflict with the notion that a protein structure is almost completely unfolded by guanidinium chloride and most of the amino acid residues in the protein interior are exposed to solvent. These results support the current view that globular proteins have some residual structures even in the unfolded state induced by a strong denaturant.
ISSN:0022-2836
DOI:10.1006/jmbi.1999.2982