How does the reductase help to regulate the catalytic cycle of cytochrome P450 3A4 using the conserved water channel?

Dan Fishelovitch, Sason Shaik, Haim J. Wolfson, Ruth Nussinov*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Water molecules play a major role in the P450 catalytic cycle. Here, we locate the preferred water pathways and their gating mechanisms for the human cytochrome P450 3A4 (CYP3A4) and elucidate the role of the cytochrome P450 reductase (CPR) in turning on and activating these water channels. We perform explicit solvent molecular dynamic simulations of CYP3A4, unbound and bound to two substrates, and with and without the flavin mononucleotide (FMN)-binding domain of CPR. We observe in/out passage of water molecules via a water-specific and conserved channel (aqueduct) located between the active site and the heme proximal side. We find that the aqueduct gating mechanism is mediated by R375, the conserved arginine that salt bridges with the heme 7-propionate. When R375 rotates, it opens the aqueduct and establishes a connection between a cluster of active site water molecules network and the bulk solvent. The aqueduct region overlaps with the CPR binding-site to CYP3A4. Indeed, we find that when the FMN domain of CPR binds to CYP3A4, the aqueduct fully opens up, thereby allowing a flow of water molecules. The aqueducts opening can permit proton transfer, shuttling the protons to the active site through ordered water molecules. In addition, the expulsion of water molecules via the aqueduct contributes to substrate binding. As such, the CPR binding has a function: it triggers the aqueducts opening and thereby enables a proton shuttle pathway, which is needed for the dioxygen activation. This mechanism could be a general paradigm in P450s.

Original languageEnglish
Pages (from-to)5964-5970
Number of pages7
JournalJournal of Physical Chemistry B
Issue number17
StatePublished - 6 May 2010


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