6EWN

HspA from Thermosynechococcus vulcanus in the presence of 2M urea with initial stages of denaturation

Summary for 6EWN

• Entry DOI: 10.2210/pdb6ewn/pdb
• Descriptor: HspA, UREA (3 entities in total)
• Functional Keywords: small heat shock protein, cyanobacteria, denaturation, urea, chaperone
• Biological source: Thermosynechococcus vulcanus (Synechococcus vulcanus)
• Total number of polymer chains: 2
• Total formula weight: 24899.75

Authors

Adir, N.,Ghosh, S.,Salama, F.,Dines, M. (deposition date: 2017-11-06, release date: 2018-10-17, Last modification date: 2024-01-17)

Primary citation

Ghosh, S.,Salama, F.,Dines, M.,Lahav, A.,Adir, N.
Biophysical and structural characterization of the small heat shock protein HspA from Thermosynechococcus vulcanus in 2 M urea.
Biochim Biophys Acta Proteins Proteom, 1867:442-452, 2019

PubMed Abstract: Small heat shock proteins (sHSPs) belong to the superfamily of molecular chaperones. They prevent aggregation of partially unfolded or misfolded client proteins, providing protection to organisms under stress conditions. Here, we report the biophysical and structural characterization of a small heat shock protein (HspA) from a thermophilic cyanobacterium Thermosynechococcus vulcanus in the presence of 2 M urea. HspA has been shown to be important for the protection of Photosystem II and the Phycobilisome antenna complex at elevated temperatures. Heterologously expressed HspA requires the presence of 1-2 M urea to maintain its solubility at concentrations required for most characterization methods. Spectroscopic studies reveal the presence of the β-sheet structure and intactness of the tertiary fold in HspA. In vitro assays show that the HspA maintains chaperone-like activity in protecting soluble proteins from thermal aggregation. Chromatography and electron microscopy show that the HspA exists as a mixture of oligomeric forms in the presence of 2 M urea. HspA was successfully crystallized only in the presence of 2 M urea. The crystal structure of HspA shows urea-induced loss of about 30% of the secondary structure without major alteration in the tertiary structure of the protein. The electron density maps reveal changes in the hydrogen bonding network which we attribute to the presence of urea. The crystal structure of HspA demonstrates a mixture of both direct interactions between urea and protein functionalities and interactions between urea and the surrounding solvent that indirectly affect the protein, which are in accordance with previously published studies.

PubMed: 30711645
DOI: 10.1016/j.bbapap.2018.12.011

Experimental method

X-RAY DIFFRACTION (2.29 Å)