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This entry represents the N-terminal domain (domain I or 'head' domain) of the magnesium chelatase H subunit (ChlH). The domain is approximately 160 residues long and is found in bacteria, archaea and eukaryotes. It is found preceding the CobN/Mg che ...
This entry represents the N-terminal domain (domain I or 'head' domain) of the magnesium chelatase H subunit (ChlH). The domain is approximately 160 residues long and is found in bacteria, archaea and eukaryotes. It is found preceding the CobN/Mg chelatase domain (Pfam:PF02514). ChlH is the catalytic subunit of magnesium chelatase (EC:6.6.1.1), which inserts Mg2+ into protoporphyrin IX to form Mg-protoporphyrin IX, the first committed step of chlorophyll biosynthesis [1,2]. In Arabidopsis thaliana, the ChlH subunit (Swiss:Q9FNB0, also known as GUN5/ABAR) is additionally involved in plastid-to-nucleus retrograde signalling and abscisic acid perception [3]. The crystal structure of ChlH from Synechocystis sp. PCC 6803 reveals that this N-terminal domain mediates dimerisation through interactions with domain V of the opposing monomer [1]. A mutation at Gly195 within this domain in Synechocystis reduces chlorophyll accumulation, consistent with a role in ChlH function or stability [4].