Alignments of SDH3 (A) and SDH4 (B) sequences.
Amino acid residues proposed for binding of protoheme IX are shown in
red and those for the quinone binding in blue. Other
conserved residues are indicated by green. Transmembrane helices
found in E. coli (Protein Data Bank code 1NEK) and porcine (Protein
Data Bank code 1ZOY) Complex II are shown by red rectangles, and
transmembrane helices predicted by TMHMM are indicated by blue
rectangles. TMHMM failed to predict transmembrane helices in T.
brucei SDH3. Residue numbers refer to E. coli SDH3 (SdhC) and
SDH4 (SdhD). GenBank™ accession numbers for SDH3 and SDH4 sequences used
are T. cruzi (XP_809410, XP_808211), T. brucei (XP_845531,
XP_823384), L. major (XP_001684890, XP_001685874), L.
infantum (XP_001467132), L. brasiliensis (XP_001566908,
XP_001567905), R. americana (NP_044796, NP_044797), Nicotiana
tobacum (YP_173376, YP_173457), Sus scrofa (1ZOY_C, 1ZOY_D), and
E. coli (NP_415249, NP_415250).