Hydrodynamic studies on the association of cytochrome P-450

Extended ultracentrifugation experiments have been performed on cytochrome P-450 LM2 from rabbit liver microsomes to analyse the behaviour of this membrane protein. The sedimentation coefficients and molecular weights vary between 11 S and 19 S and 350,000 and 700,000, respectively. No concentration dependence of these values could be observed between 0.3 microM 5.0 microM protein. The sedimentation coefficients and molecular weights appear to correlate with the heme content. Partial loss of heme leads to formation of aggregates of higher molecular weight. Analysis of the distribution of sedimentation coefficients clearly reveals the heterogeneity of the individual samples with values ranging from about 8 to 23 S. Thus, the smallest particle in the associate mixture of the enzyme consists of at most 3 monomers.