Mimicking cotranslational folding of prosubtilisin E in vitro

Area of Science:

• Protein folding
• Molecular biology
• Biochemistry

Background:

• Nascent polypeptides begin folding during synthesis on ribosomes.
• Prosubtilisin E's folding pathway involves an intramolecular chaperone (IMC).

Purpose of the Study:

• To investigate cotranslational folding intermediates of prosubtilisin E.
• To understand the role of N-terminal fragments and the IMC in protein folding.

Main Methods:

• Construction of N-terminal prosubtilisin E fragments containing an IMC.
• Analysis of secondary structures and thermostabilities of these fragments.
• Assessment of fragment behavior upon IMC truncation.

Main Results:

• IMC-containing fragments showed enhanced secondary structures and thermostability with increasing length.
• Even large fragments behaved as molten globules, indicating C-terminal region necessity for tertiary structure.
• Truncation of the IMC led to protein aggregation.

Conclusions:

• The C-terminal region is essential for achieving a stable tertiary structure in prosubtilisin.
• The IMC is critical for preventing misfolding and aggregation of cotranslational folding intermediates.