Atomic force microscopy monitoring of the temperature dependence of the cytochrome BM3 oligomeric state

Abstract

Change in temperature is one of the factors affecting the activity of enzymes. In this work, the thermal denaturation and aggregation of cytochrome P450 BM3 were studied by atomic force microscopy. The specific temperature transitions were studied by fluorescence analysis. In the low melting temperature range (10–33°C), a decrease in the fluorescence intensity of the aromatic residues was observed simultaneously with an increase in the fluorescence intensity of the flavin groups. The protein melting in this range indicated three narrow S-shaped cooperative transitions at 16, 22, and 29°C. Atomic force microscopy analysis in this temperature range showed that the BM3 molecules retained a globular shape as compact objects (heights, h < 7 nm; lateral dimensions, d < 50 nm), but the protein oligomeric state changed. The first two transitions were accompanied by a decrease in the degree of oligomerization and the third one by its increase.