Water-in-oil micro-emulsion enhances the secondary structure of a protein by confinement.
A scheme is presented in which an organic solvent environment in combination with surfactants is used to confine a natively unfolded protein inside an inverse microemulsion droplet. This type of confinement allows a study that provides unique insight into the dynamic structure of an unfolded, flexible protein which is still solvated and thus under near-physiological conditions. In a model system, the protein osteopontin (OPN) is used. It is a highly phosphorylated glycoprotein that is expressed in a wide range of cells and tissues for which limited structural analysis exists due to the high degree of flexibility and large number of post-translational modifications. OPN is implicated in tissue functions, such as inflammation and mineralisation. It also has a key function in tumour metastasis and progression. Circular dichroism measurements show that confinement enhances the secondary structural features of the protein. Small-angle X-ray scattering and dynamic light scattering show that OPN changes from being a flexible protein in aqueous solution to adopting a less flexible and more compact structure inside the microemulsion droplets. This novel approach for confining proteins while they are still hydrated may aid in studying the structure of a wide range of natively unfolded proteins.
Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Ny Munkegade 8000 Aarhus, Denmark. stepan.shipovskov@danisco.com
Stepan
S
Shipovskov
Cristiano L P
CL
Oliveira
Søren Vrønning
SV
Hoffmann
Leif
L
Schauser
Duncan S
DS
Sutherland
Flemming
F
Besenbacher
Jan Skov
JS
Pedersen
D002942:Circular Dichroism; D004655:Emulsions / Q000737:chemistry*; D008958:Models, Molecular; D009821:Oils / Q000737:chemistry*; D053495:Osteopontin / Q000737:chemistry*; D017433:Protein Structure, Secondary; D053838:Scattering, Small Angle; D014867:Water / Q000737:chemistry*; D014961:X-Ray Diffraction
D004655:Emulsions; D009821:Oils; D014867:Water; D053495:Osteopontin