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Exploring conformational preferences of proteins: ionic liquid effects on the energy landscape of avidin

DOI: 10.1039/D0SC04991C DOI Help

Authors: Talia A. Shmool (Imperial College London) , Laura K. Martin (Imperial College London) , Coby J. Clarke (Imperial College London) , Liem Bui-Le (Imperial College London) , Karen M. Polizzi (Imperial College London) , Jason P. Hallett (Imperial College London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemical Science , VOL 5

State: Published (Approved)
Published: October 2020
Diamond Proposal Number(s): 22429 , 21035 , 22514

Open Access Open Access

Abstract: In this work we experimentally investigate solvent and temperature induced conformational transitions of proteins and examine the role of ion–protein interactions in determining the conformational preferences of avidin, a homotetrameric glycoprotein, in choline-based ionic liquid (IL) solutions. Avidin was modified by surface cationisation and the addition of anionic surfactants, and the structural, thermal, and conformational stabilities of native and modified avidin were examined using dynamic light scattering, differential scanning calorimetry, and thermogravimetric analysis experiments. The protein-surfactant nanoconjugates showed higher thermostability behaviour compared to unmodified avidin, demonstrating distinct conformational ensembles. Small-angle X-ray scattering data showed that with increasing IL concentration, avidin became more compact, interpreted in the context of molecular confinement. To experimentally determine the detailed effects of IL on the energy landscape of avidin, differential scanning fluorimetry and variable temperature circular dichroism spectroscopy were performed. We show that different IL solutions can influence avidin conformation and thermal stability, and we provide insight into the effects of ILs on the folding pathways and thermodynamics of proteins. To further study the effects of ILs on avidin binding and correlate thermostability with conformational heterogeneity, we conducted a binding study. We found the ILs examined inhibited ligand binding in native avidin while enhancing binding in the modified protein, indicating ILs can influence the conformational stability of the distinct proteins differently. Significantly, this work presents a systematic strategy to explore protein conformational space and experimentally detect and characterise ‘invisible’ rare conformations using ILs.

Subject Areas: Chemistry, Biology and Bio-materials

Instruments: B21-High Throughput SAXS , B23-Circular Dichroism , I22-Small angle scattering & Diffraction

Added On: 03/11/2020 13:44


Discipline Tags:

Biochemistry Chemistry Chemical Engineering Engineering & Technology Life Sciences & Biotech

Technical Tags:

Scattering Spectroscopy Small Angle X-ray Scattering (SAXS) Circular Dichroism (CD)