Figure 6

Comparison of vertebrate SDH and SDH1 proteins. The species are: house mouse, Mus musculus, Mm; Norway rat, Rattus norvegicus, Rn; human, Homo sapiens, Hs; chicken, Gallus gallus, Gg; western clawed frog, Xenopus tropicalis, Xt; African clawed frog, Xenopus laevis, Xl; freshwater puffer fish and Tetraodon nigroviridis, Tn. By comparison with the crystal structure of rat SDH, important conserved residues found in SDH enzymes are conserved also in SDH1 and are shown above the sequence alignment. The amino acid sequence SFKIRG (blue), around the PLP binding Lys41 (pink), is conserved in SDH and SDH1. Two other conserved amino acid sequences, SAGNA (brown) and GGGGL (purple), form hydrogen bonds with PLP, as does Cys303 (green). A potassium ion near the active site is coordinated by six oxygen atoms from Gly168, Ala198, Leu223, Val225, Glu194, and Ser200 (orange). Conserved residues are indicated by a (*), strongly similar residues by a (:) and weakly similar residues by a (.). Residues are colour coded: basic, DE, red; acidic, KR, pink; polar, CGHNQSTY, green and hydrophobic, AFILMPVW, red. Exon/exon boundaries determined from genomic DNA are indicated on the proteins by black underlining. Unknown sequences are indicated by xx.