Engineering a mineralocorticoid- to a glucocorticoid-synthesizing cytochrome P450.

Site-directed mutagenesis of a domain (amino acids 299-338) aligning to the I-helix region of P450cam, P450BM3 and P450terp was used to investigate the different regioselectivities displayed in the hydroxylation reactions performed by human aldosterone synthase (P450aldo) and 11beta-hydroxylase (P45011beta). The two enzymes are 93% identical and are essential for the synthesis of mineralocorticoids and glucocorticoids in the human adrenal gland. Single replacement of P450aldo residues for P45011 beta-specific residues at positions 296, 301, 302, 320, and 335 only gave rise to slightly increased 11beta-hydroxylase activities.

Mutational effects on the spectroscopic properties and biological activities of oxidized bovine adrenodoxin, and their structural implications.

Of the aromatic 1H-NMR signals of oxidized bovine adrenodoxin only those of His56 showed intrinsic chemical shift changes upon replacement of Tyr82 by Ser or Leu, that must arise from a loss of a through-space ring-current effect of the tyrosine ring in these mutants. Thus, of the three His residues contained in adrenodoxin, His56 is closest to Tyr82, and hence to the highly acidic determinant region of adrenodoxin that is the interaction site for adrenodoxin reductase and P-450. The strong dependence of the fluorescence intensity of Tyr82 on the residue in position 56 supported this observation.

Rotamers: to be or not to be? An analysis of amino acid side-chain conformations in globular proteins.

Originally, rotamers were defined as side-chain torsion (chi-angle) combinations corresponding to the local minima of potential energy (van-der-Waals and torsion terms) for the side-chain of a terminally blocked amino acid. If at least one chi-angle differed by more than 20 degrees from that of a rotamer, the side-chain was considered as deviant both from energetic (increase in potential energy of no less than 1 to 2 kcal/mol) and geometric (precision of atom positioning is worse than 0.5 A) aspects.