Max Cryle Group - Cytochrome P450/Carrier Protein Systems

Cytochromes P450

P450s contain a cysteine ligated haem moiety at the centre of a conserved, predominantly α-helical, fold, which is able to activate molecular oxygen as an iron-oxo (ferryl) species. This species is a highly powerful oxidant and is capable of oxygen donation to substrates, in a process that often occurs with high degrees of regio- and stereoselectivity. Differences in the peptide backbone confer different substrate specificities upon the various P450s and are able to subtly vary the oxidation chemistry that they carry out. The biological roles of P450s are as varied as the reactions they catalyse: in eukaryotes they are involved in a variety of biosynthetic conversions (steroid biosynthesis), cell signaling (arachidonic acid signaling pathway) and biodegradative transformations (xenobiotic metabolism). Prokaryotic P450s have been found to catalyse a plethora of biodegradative and biosynthetic and oxidation reactions, the latter often affording molecules of medicinal significance.

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Examples of P450 substrates and the transformations that P450 enzymes can perform

© Max Cryle

The P450s are a growing superfamily of enzymes, not only in the number of identified P450s but also in the chemistry they catalyse, the substrates they bind and the manner in which they effect oxygen activation. This can be seen in the increasing number of different types of redox partners possible for P450s, the identification of P450s capable of using peroxides as oxidants via the peroxide shunt pathway and in the use of carrier proteins as scaffolds for oxidation of substrates. Carrier proteins are four helix
bundles of ~80 amino acids, found either as isolated proteins or as domains in larger multi-domain proteins, such as polyketide synthases (PKSs) and non-ribosomal peptide synthetases (NRPSs). They share a conserved serine residue that is post-translationally modified with a phosphopantetheine linker.

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Structure and post-translational modification of carrier proteins

© Max Cryle

Systems that involve the P450-catalysed oxidation of carrier protein-bound substrates are the main focus of this research group, with several specific areas of research under investigation. We are interested in the role and function of the carrier protein in such P450 systems, as well as the mechanistic aspects of P450-mediated catalysis. The techniques we use in our research are diverse and reflect the interdisciplinary nature of our department. Broadly speaking, examples
include structural biology, chemical synthesis, mass spectral analysis and biochemical assays.