This enzyme, found in green sulfur bacteria (Chlorobiaceae) and green flimentous bacteria (Chloroflexaceae), is a radical S-adenosyl-L-methionine (AdoMet) enzyme and contains a [4Fe-4S] cluster. It adds a methyl group at the C-121 position of bacteriochlorophylls of the c, d and e types. This methylation plays a role in fine-tuning the structural arrangement of the bacteriochlorophyll aggregates in chlorosomes and therefore directly influences the chlorosomes absorption properties.
Gomez Maqueo Chew, A., Frigaard, N.U. and Bryant, D.A. Bacteriochlorophyllide c C-82 and C-121 methyltransferases are essential for adaptation to low light in Chlorobaculum tepidum. J. Bacteriol.189 (2007) 6176–6184. [PMID: 17586634]