1x1a: Difference between revisions
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'''Crystal structure of BchU complexed with S-adenosyl-L-methionine''' | {{Structure | ||
|PDB= 1x1a |SIZE=350|CAPTION= <scene name='initialview01'>1x1a</scene>, resolution 2.60Å | |||
|SITE= | |||
|LIGAND= <scene name='pdbligand=SO4:SULFATE+ION'>SO4</scene>, <scene name='pdbligand=SAM:S-ADENOSYLMETHIONINE'>SAM</scene> and <scene name='pdbligand=GOL:GLYCEROL'>GOL</scene> | |||
|ACTIVITY= | |||
|GENE= | |||
}} | |||
'''Crystal structure of BchU complexed with S-adenosyl-L-methionine''' | |||
==Overview== | ==Overview== | ||
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==About this Structure== | ==About this Structure== | ||
1X1A is a [ | 1X1A is a [[Single protein]] structure of sequence from [http://en.wikipedia.org/wiki/Chlorobaculum_tepidum Chlorobaculum tepidum]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1X1A OCA]. | ||
==Reference== | ==Reference== | ||
Crystal structures of BchU, a methyltransferase involved in bacteriochlorophyll c biosynthesis, and its complex with S-adenosylhomocysteine: implications for reaction mechanism., Wada K, Yamaguchi H, Harada J, Niimi K, Osumi S, Saga Y, Oh-Oka H, Tamiaki H, Fukuyama K, J Mol Biol. 2006 Jul 21;360(4):839-49. Epub 2006 Jun 8. PMID:[http:// | Crystal structures of BchU, a methyltransferase involved in bacteriochlorophyll c biosynthesis, and its complex with S-adenosylhomocysteine: implications for reaction mechanism., Wada K, Yamaguchi H, Harada J, Niimi K, Osumi S, Saga Y, Oh-Oka H, Tamiaki H, Fukuyama K, J Mol Biol. 2006 Jul 21;360(4):839-49. Epub 2006 Jun 8. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/16797589 16797589] | ||
[[Category: Chlorobaculum tepidum]] | [[Category: Chlorobaculum tepidum]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
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[[Category: sam]] | [[Category: sam]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Mar 20 15:03:56 2008'' | ||
Revision as of 13:04, 20 March 2008
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| 1x1a, resolution 2.60Å | |||||||||||||
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| Ligands: | SO4, SAM and GOL | ||||||||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||||||||
Crystal structure of BchU complexed with S-adenosyl-L-methionine
Overview
BchU plays a role in bacteriochlorophyll c biosynthesis by catalyzing methylation at the C-20 position of cyclic tetrapyrrole chlorin using S-adenosylmethionine (SAM) as a methyl source. This methylation causes red-shifts of the electronic absorption spectrum of the light-harvesting pigment, allowing green photosynthetic bacteria to adapt to low-light environments. We have determined the crystal structures of BchU and its complex with S-adenosylhomocysteine (SAH). BchU forms a dimer and each subunit consists of two domains, an N-terminal domain and a C-terminal domain. Dimerization occurs through interactions between the N-terminal domains and the residues responsible for the catalytic reaction are in the C-terminal domain. The binding site of SAH is located in a large cavity between the two domains, where SAH is specifically recognized by many hydrogen bonds and a salt-bridge. The electron density map of BchU in complex with an analog of bacteriochlorophyll c located its central metal near the SAH-binding site, but the tetrapyrrole ring was invisible, suggesting that binding of the ring to BchU is loose and/or occupancy of the ring is low. It is likely that His290 acts as a ligand for the central metal of the substrate. The orientation of the substrate was predicted by simulation, and allows us to propose a mechanism for the BchU directed methylation: the strictly conserved Tyr246 residue acts catalytically in the direct transfer of the methyl group from SAM to the substrate through an S(N)2-like mechanism.
About this Structure
1X1A is a Single protein structure of sequence from Chlorobaculum tepidum. Full crystallographic information is available from OCA.
Reference
Crystal structures of BchU, a methyltransferase involved in bacteriochlorophyll c biosynthesis, and its complex with S-adenosylhomocysteine: implications for reaction mechanism., Wada K, Yamaguchi H, Harada J, Niimi K, Osumi S, Saga Y, Oh-Oka H, Tamiaki H, Fukuyama K, J Mol Biol. 2006 Jul 21;360(4):839-49. Epub 2006 Jun 8. PMID:16797589
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