Structural insight into human variegate porphyria disease.
Human protoporphyrinogen IX oxidase (hPPO), a mitochondrial inner membrane protein, converts protoporphyrinogen IX to protoporphyrin IX in the heme biosynthetic pathway. Mutations in the hPPO gene cause the inherited human disease variegate porphyria (VP). In this study, we report the crystal structure of hPPO in complex with the coenzyme flavin adenine dinucleotide (FAD) and the inhibitor acifluorfen at a resolution of 1.9 Å. The structural and biochemical analyses revealed the molecular details of FAD and acifluorfen binding to hPPO as well as the interactions of the substrate with hPPO. Structural analysis and gel chromatography indicated that hPPO is a monomer rather than a homodimer in vitro. The founder-effect mutation R59W in VP patients is most likely caused by a severe electrostatic hindrance in the hydrophilic binding pocket involving the bulky, hydrophobic indolyl ring of the tryptophan. Forty-seven VP-causing mutations were purified by chromatography and kinetically characterized in vitro. The effect of each mutation was demonstrated in the high-resolution crystal structure.
College of Life Science, Nankai University, Tianjin, China 300071.
Xiaohong
X
Qin
Ying
Y
Tan
Lele
L
Wang
Zhifang
Z
Wang
Baifan
B
Wang
Xin
X
Wen
Guangfu
G
Yang
Zhen
Z
Xi
Yuequan
Y
Shen
D000595:Amino Acid Sequence; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D046350:Porphyria, Variegate / Q000235:genetics*; D011485:Protein Binding; D011487:Protein Conformation; D050768:Protoporphyrinogen Oxidase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D005182:Flavin-Adenine Dinucleotide; D050768:Protoporphyrinogen Oxidase