2fcr
|
CRYSTAL STRUCTURE OF OXIDIZED FLAVODOXIN FROM A RED ALGA CHONDRUS CRISPUS REFINED AT 1.8 ANGSTROMS RESOLUTION: DESCRIPTION OF THE FLAVIN MONONUCLEOTIDE BINDING SITE
OverviewOverview
In order to describe the detailed conformation of the oxidized flavodoxin, from a eukaryotic red alga, Chondrus crispus, the crystal structure has, been refined by a restrained least-squares method. The crystallographic R, factor is 0.168 for 13,899 reflections with F greater than 2 sigma F, between 6.0 and 1.8 A resolution. The refined model includes 173 amino, acid residues, flavin mononucleotide (FMN) and 110 water molecules. The, root-mean-square deviation in bond lengths from ideal values is 0.015 A, and the mean co-ordinate error is estimated to be 0.2 A. The FMN is, located at the periphery of the molecule. The orientation of the, isoalloxazine ring is such that the C-7 and C-8 methyl groups are exposed, to solvent and the pyrimidine moiety is buried in the protein. Three, peptide segments, T8-T13, T55-T58 and D94-C103, are involved in FMN, binding. The first segment of T8-T13 enfolds the phosphate group of the, FMN. The three oxygen atoms in the phosphate group form extensive hydrogen, bonds with amide groups of the main chain and the O gamma atoms of the, side-chains in this segment. T55 O and W56 N epsilon 1 in the second, segment form hydrogen bonds with O-2 in the ribityl moiety and one of the, oxygen atoms in the phosphate group, respectively. The O gamma H of T58, forms a hydrogen bond with the N-5 atom in the isoalloxazine ring, which, is expected to be protonated in the semiquinone form. The third segment is, in contact with the isoalloxazine ring. It appears that the hydrogen bond, acceptor of the NH of Asp94 in the third segment is O-2 rather than N-1 in, the isoalloxazine ring. The isoalloxazine ring is flanked by the, side-chains of Trp56 and Tyr98; it forms an angle of 38 degrees with the, indole ring of Trp56 and is almost parallel to the benzene ring of Tyr98., The environment of the phosphate group is conserved as in other, flavodoxins whereas that of the isoalloxazine ring differs. The, relationship between the hydrogen bond to the N-5 in the ring and the, redox potential for the oxidized/semiquinone couple is discussed.
About this StructureAbout this Structure
2FCR is a Single protein structure of sequence from Chondrus crispus with FMN as ligand. Full crystallographic information is available from OCA.
ReferenceReference
Crystal structure of oxidized flavodoxin from a red alga Chondrus crispus refined at 1.8 A resolution. Description of the flavin mononucleotide binding site., Fukuyama K, Matsubara H, Rogers LJ, J Mol Biol. 1992 Jun 5;225(3):775-89. PMID:1602481
Page seeded by OCA on Wed Nov 21 10:29:07 2007