Cytochrome P-450: hexameric structure of the purified LM4 form

Purified cytochrome P-450_LM4 was found to be monodisperse in 20% glycerol by analytical ultracentrifugation. Its S_20,w value was quite similar to that of hexameric P-450_LM2. At lower glycerol concentrations the P-450_LM4 oligomers showed a tendency to aggregate. The P-450_LM4 oligomers were immobilized on Ultrogel A4 under conditions allowing only one covalent link to the matrix per oligomer. In the presence of SDS, the oligomers dissociated leaving only 1 6th of the initial amount of bound protein on the matrix, suggesting that the purified P-450_LM4 is a hexamer. This was confirmed by electron microscopy. The quaternary structure of the P-450_LM4 was similar to that demonstrated earlier for P-450_LM2.