Evolution of Function in the “Two Dinucleotide Binding Domains” Flavoproteins
Figure 6
Quaternary Structures of Members of the tDBDF Superfamily
(I) Illustration showing the four main types of quaternary structures observed. F, FAD; N, NAD(P)H; A represents a domain that assists in binding small molecules that accept two electrons and/or presents two cysteine residues that can transfer electrons to external electron acceptors; A* represents a domain or protein that accepts one electron at a time using heme or an iron-sulfur cluster.
(II) Structural superimposition showing the quaternary structures of some divergent members of the tDBDF superfamily. tDBDF domains are shown in gray. The C-terminal domains of the members of the DSR and NDH subgroups are not shown for ease of viewing. Colors and PDB identifiers are as follows. A) DSR subgroup: dark red, glutathione reductase (1get); sea green, 2-ketopropyl coenzyme M oxidoreductase/carboxylase (1mo9); orange, mercuric reductase. POR subgroup: chartreuse, CoA Disulfide Reductase (1yqz). B) AHR subgroup: purple, E Coli thioredoxin reductase (1f6m). C) NDH subgroup: magenta, cytochrome c sulfide dehydrogenase (1fcd). ADR subgroup: goldenrod, adrenodoxin reductase (1e6e). D) DCR subgroup: forest green, 2,4-dienoylCoA reductase (1ps9). GMS subgroup: coral, dihydropyrimidine dehydrogenase (1gte).