Denaturation of apolipoprotein A-I and the monomer form of apolipoprotein A-I(Milano).
In this study the thermal and denaturant induced unfolding of apolipoprotein A-I (apo A-I) and the monomer form of apolipoprotein A-I(Milano) (apo A-I(M)) was followed. Dimer apo A-I(M) was reduced with dithiothreitol, which was present in the protein solutions in all experiments. Thermal denaturation is followed by differential scanning calorimetry (DSC) and far-UV and near-UV CD. Both apo A-I and monomer apo A-IM have a broad asymmetric DSC peak that could be deconvoluted into three non two-state transitions, apo A-I being more stable than the monomer apo A-IM. Estimation of melting of tertiary structure by near-UV CD is lower than that for secondary structure determined from far-UV. This together with the non two-state unfolding of the proteins observed with DSC is indicative of unfolding via a molten globular-like state. Apo A-I and monomer apo A-I(M) are equally susceptible to guanidinum chloride, half-unfolded at 1.2 M denaturant. The presence of 0.5 and 1.0 M denaturant, lower and equalize the denaturation temperatures of the proteins, respectively.
Suurkuusk
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M
Department of Structural Chemistry, Pharmacia & Upjohn, Stockholm, Sweden. malin.suurkuusk@thermometric.se
Hallén
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D
D016632:Apolipoprotein A-I / Q000737:chemistry* / Q000235:genetics*; D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D004229:Dithiothreitol; D014644:Genetic Variation; D019791:Guanidine; D006358:Hot Temperature; D006801:Humans; D008956:Models, Chemical; D010084:Oxidation-Reduction; D011489:Protein Denaturation; D020836:Protein Structure, Quaternary; D014466:Ultraviolet Rays
D016632:Apolipoprotein A-I; C080631:apolipoprotein A-I Milano; D019791:Guanidine; D004229:Dithiothreitol