Reassembly of an Integral Oligomeric Membrane Protein OmpF Porin in n-octyl β-d-Glucopyranoside–Lipids Mixtures

Abstract

The denatured monomers of an integral membrane protein OmpF porin were refolded and reassembled into its sodium dodecyl sulfate-resistant trimer in mixtures of n-octyl beta-D: -glucopyranoside and lipids. Effective reassembly was observed with a yield of 60-70% when the denatured monomers (0.1 mg/mL) were solubilized at 25 degrees C for 24 h in a refolding medium (pH 6.9) containing 7 mg/mL n-octyl beta-D: -glucopyranoside, 1 mg/mL sodium dodecyl sulfate and 2-2.5 mg/mL soybean asolectin. The reassembled species was characterized in the presence of sodium dodecyl sulfate by physicochemical methods. Low-angle laser light scattering measurements revealed that the molecular weight of the reassembled species is 115,000 +/- 3,500 which corresponds to that of the trimer of this protein. Circular dichroism spectra suggested that the reassembled species is composed of the same beta-structure as the native one. Synchrotron radiation small-angle X-ray scattering measurements confirmed that the reassembled species is a trimer that has the same compactness as the native one.