Catalytically Relevant Electrostatic Interactions of Cytochrome P450c17 (CYP17A1) and Cytochrome b5

Recent Structural Insights into Cytochrome P450 Function

“…The NMR evidence is supportive of roles of NADPH-P450 reductase and cytochrome b 5 in modulating the conformations. The NMR data also argue that these two accessory proteins occupy the same site on P450 17A1 and compete for space [104–106] (Figure 6A). In light of the evidence that cytochrome b 5 does not enhance activity by electron transfer [102], the mechanism of stimulation remains enigmatic: in principle, the reductase transfers two electrons into the Fe/FeO system (generating a very reactive complex), it dissociates, cytochrome b 5 binds and changes the conformation, the reaction occurs, and then cytochrome b 5 (and the reaction product) dissociate (so that the reductase can bind again).…”

“…(A) Surface representation of the complex between human P450 17A1 (gray) and cytochrome b 5 (beige) based on cross-linking and mass spectrometric analysis [106]. The model was generated with the program HADDOCK [108], using the X-ray coordinates of human 17A1 (PDB 3RUK) [100] and NMR coordinates of human b 5 (PDB 2I96).…”

Role of Protein-Protein Interactions in Metabolism: Genetics, Structure, Function

“…In this complex, it became clear that shortening the CPR hinge region leads to a protein that favors the open conformation and promotes association with HO (Sugishima et al, 2014). These studies demonstrate the utility of combining the power of Sevrioukova et al, 1997Cupp-Vickery et al, 2000;Hall et al, 2001;Podust et al, 2001;Yoshinari et al, 2001;Williams et al, 2003;Grahn et al, 2006;He et al, 2006;Deng et al, 2010;Wilderman et al, 2012;Hiruma et al, 2013;Tripathi et al, 2013;Peng et al, 2014;Sugishima et al, 2014;Basudhar et al, 2015;Reed and Backes, 2017;Gill, 1983;Kakuta et al, 1997;Meech and Mackenzie, 1997;Argiriadi et al, 1999;Binda et al, 2001Binda et al, , 2011…”

“…X-ray crystallography has also been useful for dissecting the protein-protein interactions of another CYP electron transfer partner, b 5 . Using a combination of chemical crosslinking and protein crystal structures, Peng et al were able to propose a model for the b 5 mediated stimulation of the 17,20-lyase activity of cytochrome P450c17 (Peng et al, 2014), suggesting that electrostatic interactions predominate in the CYP-b5 interaction, as they do with the CYP-CPR complex. In another example, X-ray crystal structures of b 5 have informed our understanding of electron transfer from b 5 to individual CYPs, such as CYP2B4, where ligand-induced structural changes were found to be coupled to b 5 effector binding .…”

Structural and Kinetic Basis of Steroid 17α,20-Lyase Activity in Teleost Fish Cytochrome P450 17A1 and Its Absence in Cytochrome P450 17A2

“…We propose that this amino acid residue of P450 17A1 is necessary for the lyase activity (although others may also cause this) and that multiple substitutions of P450 17A2 are probably needed to confer lyase activity to this protein. Human P450 17A1 Arg-358 has been implicated in b 5 binding through NMR, chemical cross-linking, and other techniques (59,72,73). However, zebrafish P450 17A1 shows only ϳ2-fold stimulation by b 5 (Fig.…”