Crystal structure of human gamma-butyrobetaine hydroxylase.
Gamma-butyrobetaine hydroxylase (GBBH) is a 2-ketoglutarate-dependent dioxygenase that catalyzes the biosynthesis of l-carnitine by hydroxylation of gamma-butyrobetaine (GBB). l-carnitine is required for the transport of long-chain fatty acids into mitochondria for generating metabolic energy. The only known synthetic inhibitor of GBBH is mildronate (3-(2,2,2-trimethylhydrazinium) propionate dihydrate), which is a non-hydroxylatable analog of GBB. To aid in the discovery of novel GBBH inhibitors by rational drug design, we have solved the three-dimensional structure of recombinant human GBBH at 2.0A resolution. The GBBH monomer consists of a catalytic double-stranded beta-helix (DBSH) domain, which is found in all 2KG oxygenases, and a smaller N-terminal domain. Extensive interactions between two monomers confirm earlier observations that GBBH is dimeric in its biological state. Although many 2KG oxygenases are multimeric, the dimerization interface of GBBH is very different from that of related enzymes. The N-terminal domain of GBBH has a similar fold to the DUF971 superfamily, which consists of several short bacterial proteins with unknown function. The N-terminal domain has a bound Zn ion, which is coordinated by three cysteines and one histidine. Although several other 2KG oxygenases with known structures have more than one domain, none of them resemble the N-terminal domain of GBBH. The N-terminal domain may facilitate dimer formation, but its precise biological role remains to be discovered. The active site of the catalytic domain of GBBH is similar to that of other 2KG oxygenases, and Fe(II)-binding residues form a conserved His-X-Asp-X(n)-His triad, which is found in all related enzymes.
Tars
Kaspars
K
Biomedical Research and Study Centre, Ratsupites 1, LV1067, Riga, Latvia. kaspars@biomed.lu.lv
Rumnieks
Janis
J
Zeltins
Andris
A
Kazaks
Andris
A
Kotelovica
Svetlana
S
Leonciks
Ainars
A
Sharipo
Jelena
J
Viksna
Arturs
A
Kuka
Janis
J
Liepinsh
Edgars
E
Dambrova
Maija
M
D020134:Catalytic Domain; D003461:Crystallography; D015195:Drug Design; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D008763:Methylhydrazines / Q000494:pharmacology; D055503:Protein Multimerization; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D015032:Zinc / Q000737:chemistry; D050563:gamma-Butyrobetaine Dioxygenase / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics
D004791:Enzyme Inhibitors; D008763:Methylhydrazines; D011994:Recombinant Proteins; C050147:3-(2,2,2-trimethylhydrazine)propionate; D050563:gamma-Butyrobetaine Dioxygenase; D015032:Zinc