The yeast Hsp110, Sse1p, exhibits high-affinity peptide binding

Area of Science:

• Molecular Biology
• Protein Biochemistry
• Chaperone Proteins

Background:

• Heat shock proteins (Hsp) 110 are ATP-hydrolyzing relatives of Hsp70 chaperones.
• Hsp110s function as Hsp70 nucleotide exchange factors and directly maintain polypeptide solubility.
• The effect of peptide binding on Hsp110 ATPase activity and affinity remains uncharacterized.

Purpose of the Study:

• To investigate the impact of peptide binding on the ATPase activity of yeast Hsp110 (Sse1p).
• To measure the binding affinity of a specific peptide to Sse1p.
• To explore potential differences in peptide recognition between Hsp70 and Hsp110 chaperones.

Main Methods:

• Characterization of peptide binding to Sse1p using binding assays.
• Measurement of Sse1p ATPase activity in the presence of bound peptides.
• Comparative analysis of peptide binding to Sse1p and Hsp70.

Main Results:

• A specific peptide was found to bind yeast Sse1p with a dissociation constant (K(D)) of approximately 2 nM.
• Surprisingly, this peptide binding did not stimulate Sse1p's ATP hydrolysis activity.
• A known Hsp70-binding peptide did not bind to Sse1p, indicating distinct peptide-binding specificities.

Conclusions:

• Hsp110s (Sse1p) exhibit high-affinity peptide binding independent of ATPase stimulation.
• Hsp70 and Hsp110 chaperones possess partially distinct peptide recognition motifs.
• These findings provide new insights into the functional divergence of Hsp70 and Hsp110 chaperone families.