4QDJ: Crystal Structure Of Magnesium Protoporphyrin Ix Methyltransferase (chlm) From Synechocystis Pcc 6803 With Bound Sam

Magnesium protoporphyrin IX O-methyltransferase (ChlM) catalyzes transfer of the methyl group from S-adenosylmethionine to the carboxyl group of the C13 propionate side chain of magnesium protoporphyrin IX. This reaction is the second committed step in chlorophyll biosynthesis from protoporphyrin IX. Here we report the crystal structures of ChlM from the cyanobacterium Synechocystis sp. PCC 6803 in complex with S-adenosylmethionine and S-adenosylhomocysteine at resolutions of 1.6 and 1.7 A, respectively. The structures illustrate the molecular basis for cofactor and substrate binding and suggest that conformational changes of the two "arm" regions may modulate binding and release of substrates/products to and from the active site. Tyr-28 and His-139 were identified to play essential roles for methyl transfer reaction but are not indispensable for cofactor/substrate binding. Based on these structural and functional findings, a catalytic model is proposed.
PDB ID: 4QDJDownload
MMDB ID: 122209
PDB Deposition Date: 2014/5/14
Updated in MMDB: 2015/08
Experimental Method:
x-ray diffraction
Resolution: 1.6  Å
Source Organism:
Similar Structures:
Biological Unit for 4QDJ: monomeric; determined by author and by software (PISA)
Molecular Components in 4QDJ
Label Count Molecule
Protein (1 molecule)
Magnesium-protoporphyrin O-methyltransferase
Molecule annotation
Chemicals (2 molecules)
* Click molecule labels to explore molecular sequence information.

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