InterPro domain: IPR000523

This domain can be found in the magnesium chelatase ChlI subunit, the catalytic domain that binds and hydrolyses ATP. This domain contains the nucleotide binding Walker motif [ 1 ] and can also be found in the competence protein ComM from Haemophilus influenzae and Lon proteases from archaea.

Magnesium-chelatase is a three-component enzyme that catalyses the insertion of Mg ²⁺ into protoporphyrin IX. This is the first unique step in the synthesis of (bacterio)chlorophyll. As a result, it is thought that Mg-chelatase has an important role in channeling intermediates into the (bacterio)chlorophyll branch in response to conditions suitable for photosynthetic growth. ChlI and BchD have molecular weights between 38-42kDa [ 2 , 3 ].

1. The CHLI1 subunit of Arabidopsis thaliana magnesium chelatase is a target protein of the chloroplast thioredoxin. J Biol Chem 282, 19282-91
2. Mechanism and regulation of Mg-chelatase. Biochem. J. 327 ( Pt 2), 321-33
3. Reconstitution of an active magnesium chelatase enzyme complex from the bchI, -D, and -H gene products of the green sulfur bacterium Chlorobium vibrioforme expressed in Escherichia coli. J. Bacteriol. 180, 699-704