Crystallization of a designed peptide from a molten globule ensemble

Area of Science:

• Protein engineering
• Biophysics
• Structural biology

Background:

• Designing amino acid sequences for specific protein folds remains challenging.
• Previously designed proteins often exhibit molten globule states, crucial for understanding protein folding.
• Molten globule states are compact, non-native conformations important for protein stability.

Purpose of the Study:

• To characterize peptides designed to form alpha-helical aggregates.
• To determine if crystalline conformations are retained in solution.
• To investigate the solution behavior of peptides forming molten globular ensembles.

Main Methods:

• Peptide design and synthesis (16-residue alpha1A and related alpha1).
• Solid-state characterization (X-ray crystallography).
• Solution-state characterization (NMR spectroscopy, sedimentation equilibria, thermal unfolding, ANS binding).

Main Results:

• Crystals of peptide alpha1A diffracted to 3.5 Å resolution.
• Solution studies indicated peptides form alpha-helical aggregates resembling molten globule states.
• Peptides rapidly adopted compact molten globular states upon dissolution, similar to folding intermediates.

Conclusions:

• Crystallization of these designed peptides mirrors aspects of natural protein folding.
• The peptides' behavior in solution provides a model for molten globule intermediates.
• Understanding these states is critical for advancing protein design and folding studies.