Crystal Structure of NADH-cytochrome b₅Reductase and Electron Transfer in Flavin-dependent Reductases

Abstract

The structure of NADH-cytochrome bs reductase has been determined and refined at 2.1 Å resolution. The molecular structure reveals its two domain nature, the FAD binding domain and the NADH domain. Structural difference between the FAD-binding site of this enzyme and that of ferredoxin-NADP⁺ reductase gives an explanation about the difference of their enzymatic reaction with nucleotides. Three conserved amino acid residues interact significantly with the flavin molecules in four flavin-dependent reductases whose molecular structures have a similar folding pattern in spite of their relative low sequence identity. The electrostatic potentials on the molecular surfaces were compared among these four flavin-dependent reductases and their electron-transfer partners.