Physical and chemical properties of Δ3−12 cysteine-depleted cytocrome P450 3A4 with amino acid substitution of S291C

Abstract

Cytochrome P450 3A4 (3A4) is highly expressed in the human liver cells and plays a decisive role in the metabolism of xenobiotics, including more than 50 % of medical products. The activity of this enzyme can be regulated at the expression level of genes, as well as at the conformation level of the structure of the protein itself, due to changes in the molecular environment, including due to the interaction with high-molecular effectors. The understanding of the structure changes and the 3A4 dynamics in response to the environmental changes is necessary to predict the changes in the level of its activity that to a considerable extent regulates the body’s homeostasis. To perform in vitro experiments on the structure, dynamics, and protein-ligand/protein interactions of the enzymes by the modern spectral methods, the approach is used, in which the target protein is selectively added with cysteine residues in the given polypeptide chain loci by the protein engineering methods for subsequent labeling with specialized molecular labels. To do this, the human mutant form of membrane-bound (full length) recombinant cytochrome P450 3A4 C58A/C64M/C98A/C239T/C377A/C468S/S291C was obtained. According to the circular dichroism spectroscopy data we established that the introduced mutations do not cause significant changes in the secondary structure of the obtained form 3A4, which shows the preservation of the folding of the peptide chain. The spectral photometric measurements were made to comparatively analyze the changes in the affinity to the ligands of the active center. Moreover, we showed that the testosterone hydroxylase activity in the in vitro reconstructed system for a given mutation form of 3A4 increases many times with respect to the wild form of the enzyme.