1PJZ

Solution structure of thiopurine methyltransferase from Pseudomonas syringae

Summary for 1PJZ

• Entry DOI: 10.2210/pdb1pjz/pdb
• NMR Information: BMRB: 5820
• Descriptor: Thiopurine S-methyltransferase (1 entity in total)
• Functional Keywords: methyltransferase, polymorphism, s-adenosylmethionine, drug metabolism, transferase
• Biological source: Pseudomonas syringae pv. pisi
• Cellular location: Cytoplasm: O86262
• Total number of polymer chains: 1
• Total formula weight: 22590.49

Authors

Scheuermann, T.H.,Lolis, E.,Hodsdon, M.E. (deposition date: 2003-06-04, release date: 2003-10-14, Last modification date: 2024-05-22)

Primary citation

Scheuermann, T.H.,Lolis, E.,Hodsdon, M.E.
Tertiary structure of thiopurine methyltransferase from Pseudomonas syringae, a bacterial orthologue of a polymorphic, drug-metabolizing enzyme
J.Mol.Biol., 333:573-585, 2003

PubMed Abstract: In humans, the enzyme thiopurine methyltransferase (TPMT) metabolizes 6-thiopurine (6-TP) medications, including 6-thioguanine, 6-mercaptopurine and azathioprine, commonly used for immune suppression and for the treatment of hematopoietic malignancies. S-Methylation by TPMT prevents the intracellular conversion of these drugs into active 6-thioguanine nucleotides (6-TGNs). Genetic polymorphisms in the TPMT protein sequence have been associated with decreased tissue enzymatic activities and an increased risk of life-threatening myelo-suppression from standard doses of 6-TP medications. Biochemical studies have demonstrated that TPMT deficiency is primarily associated with increased degradation of the polymorphic proteins through an ubiquitylation and proteasomal-dependent pathway. We have now determined the tertiary structure of the bacterial orthologue of TPMT from Pseudomonas syringae using NMR spectroscopy. Bacterial TPMT similarly catalyzes the S-adenosylmethionine (SAM)-dependent transmethylation of 6-TPs and shares 45% similarity (33% identity) with the human enzyme. Initial studies revealed an unstructured N terminus, which was removed for structural studies and subsequently determined to be required for enzymatic activity. Despite lacking sequence similarity to any protein of known three-dimensional structure, the tertiary structure of bacterial TPMT reveals a classical SAM-dependent methyltransferase topology, consisting of a seven-stranded beta-sheet flanked by alpha-helices on both sides. However, some deviations from the consensus topology, along with multiple insertions of structural elements, are evident. A review of the many experimentally determined tertiary structures of SAM-dependent methyltransferases demonstrates that such structural deviations from the consensus topology are common and often functionally important.

PubMed: 14556746
DOI: 10.1016/j.jmb.2003.08.039

Experimental method

SOLUTION NMR