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Search The CSA
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Catalytic Site Atlas

CSA LITERATURE entry for 1g8p

E.C. namemagnesium chelatase
SpeciesRhodobacter capsulatus (strain ATCC BAA-309 / NBRC 16581 / SB1003)
E.C. Number (IntEnz) 6.6.1.1
CSA Homologues of 1g8pThere are 10 Homologs
CSA Entries With UniProtID P26239
CSA Entries With EC Number 6.6.1.1
PDBe Entry 1g8p
PDBSum Entry 1g8p
MACiE Entry 1g8p

Literature Report

IntroductionMagnesium Chelatase has a vital role in chlorophyll biosynthesis, using the energy from ATP hydrolysis to insert a Mg2+ ion into a porphyrin ring. It is part of a generic family of cellular ATPases known as AAA, displaying homology in particular to Cobalt Chelatase. Three subunits make up the overall protein, and the catalytic residues described all refer to the ATP hydrolysing subunit BchI.
MechansimBinding of the porphyrin and the Magnesium triggers the release of the ATP binding site of the BChI subunit which is able to hydrolyse ATP. The hydrolysis of ATP proceeds via the nucleophilic attack of a water molecule on the gamma phosphate, to form a pentavalent transition state stabilised by Arg 289. This collapses to release the products ADP and Pi, causing subunit motion which results in the transfer of Mg2+ to the porphyrin.
Reaction

Catalytic Sites for 1g8p

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
ArgA289289macie:sideChainThe protonated side chain of Arg 289 acts to stabilise the pentavalent phosphate transition state through electrostatic interaction. The transition state then collapses to release the products resulting in ATP hydrolysis.

Literature References

Notes:
Fodje MN
Interplay between an AAA module and an integrin I domain may regulate the function of magnesium chelatase.
J Mol Biol 2001 311 111-122
PubMed: 11469861
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