Polymorphism on human aromatase affects protein dynamics and substrate binding: spectroscopic evidence

Abstract Human aromatase is a member of the cytochrome P450 superfamily, involved in steroid hormones biosynthesis. In particular, it converts androgen into estrogens being therefore responsible for correct sex steroids balance. Due to its capacity producing has also been considered as promising target breast cancer therapy. Two single-nucleotide polymorphisms (R264C and R264H) have shown alter activity they associated an increased or decreased risk estrogen-dependent pathologies. Here, effect these mutations on protein dynamics investigated by UV/FTIR time resolved fluorescence spectroscopy. H/D exchange rates were measured FTIR three proteins ligand-free, substrate- inhibitor-bound forms data indicate that wild-type enzyme undergoes conformational change leading more compact tertiary structure upon substrate inhibitor binding. Indeed, are when ligand present. variants, ligand-free –bound similar, indicating structural lacking, despite single amino acid substitution located peripheral shell molecule. Moreover, lifetimes show quenching tryptophan-224 observed binding wild-type, absent both variants. Since this residue catalytic pocket, findings suggest entrance and/or retention active site partially compromised mutants. A contact network analysis demonstrates organized two main clusters, whose connectivity altered binding, especially correspondence helix-G, where substitutions occur. Our demonstrate SNPs resulting surface modify flexibility required catalysis. The cluster provides rationale such effect, suggesting helix G possible inhibition.