Download MendeleyNew aspects of electron transfer revealed by the crystal structure of a truncated bovine adrenodoxin, Adx(4-108).
Muller, A., Muller, J.J., Muller, Y.A., Uhlmann, H., Bernhardt, R., Heinemann, U.(1998) Structure 6: 269-280
- PubMed: 9551550
- DOI: https://doi.org/10.1016/s0969-2126(98)00031-8
- Primary Citation of Related Structures:
1AYF - PubMed Abstract:
Adrenodoxin (Adx) is a [2Fe-2S] ferredoxin involved in steroid hormone biosynthesis in the adrenal gland mitochondrial matrix of mammals. Adx is a small soluble protein that transfers electrons from adrenodoxin reductase (AR) to different cytochrome P450 isoforms where they are consumed in hydroxylation reactions. A crystallographic study of Adx is expected to reveal the structural basis for an important electron transfer reaction mediated by a vertebrate [2Fe-2S] ferredoxin. The crystal structure of a truncated bovine adrenodoxin, Adx(4-108), was determined at 1.85 A resolution and refined to a crystallographic R value of 0.195. The structure was determined using multiple wavelength anomalous dispersion phasing techniques, making use of the iron atoms in the [2Fe-2S] cluster of the protein. The protein displays the compact (alpha + beta) fold typical for [2Fe-2S] ferredoxins. The polypeptide chain is organized into a large core domain and a smaller interaction domain which comprises 35 residues, including all those previously determined to be involved in binding to AR and cytochrome P450. A small interdomain motion is observed as a structural difference between the two independent molecules in the asymmetric unit of the crystal. Charged residues of Adx(4-108) are clustered to yield a strikingly asymmetric electric potential of the protein molecule. The crystal structure of Adx(4-108) provides the first detailed description of a vertebrate [2Fe-2S] ferredoxin and serves to explain a large body of biochemical studies in terms of a three-dimensional structure. The structure suggests how a change in the redox state of the [2Fe-2S] cluster may be coupled to a domain motion of the protein. It seems likely that the clearly asymmetric charge distribution on the surface of Adx(4-108) and the resulting strong molecular dipole are involved in electrostatic steering of the interactions with AR and cytochrome P450.
Organizational Affiliation:
Forschungsgruppe Kristallographie, Max-Delbr¨¹ck-Centrum f¨¹r Molekulare Medizin, Berlin, Germany.
