1pv8
Crystal structure of a low activity F12L mutant of human porphobilinogen synthase
Structural highlights
DiseaseHEM2_HUMAN Defects in ALAD are the cause of acute hepatic porphyria (AHEPP) [MIM:612740. A form of porphyria. Porphyrias are inherited defects in the biosynthesis of heme, resulting in the accumulation and increased excretion of porphyrins or porphyrin precursors. They are classified as erythropoietic or hepatic, depending on whether the enzyme deficiency occurs in red blood cells or in the liver. AHP is characterized by attacks of gastrointestinal disturbances, abdominal colic, paralysis, and peripheral neuropathy. Most attacks are precipitated by drugs, alcohol, caloric deprivation, infections, or endocrine factors.[1] [2] [3] [4] [5] FunctionHEM2_HUMAN Catalyzes an early step in the biosynthesis of tetrapyrroles. Binds two molecules of 5-aminolevulinate per subunit, each at a distinct site, and catalyzes their condensation to form porphobilinogen.[6] [7] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedPorphobilinogen synthase (PBGS) catalyzes the first common step in the biosynthesis of tetrapyrroles (such as heme and chlorophyll). Although the predominant oligomeric form of this enzyme, as inferred from many crystal structures, is that of a homo-octamer, a rare human PBGS allele, F12L, reveals the presence of a hexameric form. Rearrangement of an N-terminal arm is responsible for this oligomeric switch, which results in profound changes in kinetic behavior. The structural transition between octamer and hexamer must proceed through an unparalleled equilibrium containing two different dimer structures. The allosteric magnesium, present in most PBGS, has a binding site in the octamer but not in the hexamer. The unprecedented structural rearrangement reported here relates to the allosteric regulation of PBGS and suggests that alternative PBGS oligomers may function in a magnesium-dependent regulation of tetrapyrrole biosynthesis in plants and some bacteria. Control of tetrapyrrole biosynthesis by alternate quaternary forms of porphobilinogen synthase.,Breinig S, Kervinen J, Stith L, Wasson AS, Fairman R, Wlodawer A, Zdanov A, Jaffe EK Nat Struct Biol. 2003 Sep;10(9):757-63. Epub 2003 Aug 3. PMID:12897770[8] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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