Application of AFM and optical biosensor for investigation of complexes formed in P450-containing monooxygenase systems

Atomic force microscopy (AFM) allows to visualize and count the individual protein molecules and their complexes within multiprotein systems. On the other hand, optical biosensor (OB) provides information on complex formation kinetics as well as complex lifetime (τLT) and affinity. Comparison of complex lifetime τLT with the time required for enzyme's catalytic cycle (τcat) enables to characterize productive complexes and distinguish them from non-productive ones. Both these approaches were applied for the analysis of the three cytochrome P450-containing monooxygenase systems: cytochrome P450 101, cytochrome P450 11A1 and cytochrome P450 2B4. By using AFM, the formation of binary and ternary protein complexes was registered in all the three systems. OB analysis enabled to kinetically characterize these binary and ternary complexes. It was shown that the binary complexes putidaredoxin reductase (PdR)/putidaredoxin (Pd) and Pd/cytochrome P450 101 (P450 101) formed within the P450 101 system and, also, the binary complexes adrenodoxin reductase (AdR)/adrenodoxin (Ad) and Ad/cytochrome P450 11A1 (P450 11A1) formed within the P450 11A1 system are non-productive (deadlock). At the same time, the ternary PdR/Pd/P450 101 and AdR/Ad/P450 11A1 complexes proved to be productive. The binary cytochrome P450 reductase (Fp)/cytochrome P450 2B4 (2B4) complexes and the ternary Fp/2B4/cytochrome b5 (b5) complexes formed within P450 2B4 system were productive.