Folding intermediates of beta-lactamase recognized by GroEL

Area of Science:

• Biochemistry
• Molecular Biology
• Protein Folding

Background:

• Protein folding is a complex process crucial for biological function.
• Chaperones like GroEL assist in protein folding by preventing aggregation.
• Disulfide bonds can influence protein folding pathways and stability.

Purpose of the Study:

• To investigate the role of disulfide bonds in beta-lactamase folding.
• To determine the interaction of wild-type and mutant beta-lactamase with GroEL during folding.

Main Methods:

• Site-directed mutagenesis to remove disulfide bonds in beta-lactamase (Cys-->Ala mutations).
• Analysis of beta-lactamase folding kinetics using 3-phasic kinetics.
• Assessment of complex formation between beta-lactamase variants and GroEL over time.

Main Results:

• Mutant beta-lactamase lacking a disulfide bond formed stable complexes with GroEL within the first 30 seconds of folding.
• Wild-type beta-lactamase, containing a disulfide bond, did not form stable complexes with GroEL under the same conditions.
• Folding kinetics were similar for both wild-type and mutant beta-lactamase, with enzymatic activity observed late in the process.

Conclusions:

• GroEL is unable to bind late folding intermediates of beta-lactamase.
• The presence or absence of a disulfide bond significantly affects GroEL binding during early folding stages.
• GroEL discriminates between different unfolding extents in wild-type and mutant beta-lactamase.