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| - | [[Image:1x1a.gif|left|200px]] | + | {{Seed}} |
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| | {{STRUCTURE_1x1a| PDB=1x1a | SCENE= }} | | {{STRUCTURE_1x1a| PDB=1x1a | SCENE= }} |
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| - | '''Crystal structure of BchU complexed with S-adenosyl-L-methionine'''
| + | ===Crystal structure of BchU complexed with S-adenosyl-L-methionine=== |
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| - | ==Overview==
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| - | 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.
| + | The line below this paragraph, {{ABSTRACT_PUBMED_16797589}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 16797589 is the PubMed ID number. |
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| | + | {{ABSTRACT_PUBMED_16797589}} |
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| | ==About this Structure== | | ==About this Structure== |
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| | [[Category: Sah]] | | [[Category: Sah]] |
| | [[Category: Sam]] | | [[Category: Sam]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 14:24:10 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 07:05:38 2008'' |
Revision as of 04:05, 28 July 2008
Template:STRUCTURE 1x1a
Crystal structure of BchU complexed with S-adenosyl-L-methionine
Template:ABSTRACT PUBMED 16797589
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
Page seeded by OCA on Mon Jul 28 07:05:38 2008
