title: Heterologous expression of the bchM gene product from Rhodobacter capsulatus and demonstration that it encodes S-adenosyl-L-methionine:Mg-protoporphyrin IX methyltransferase.
abstract: The bacteriochlorophyll biosynthesis gene, bchM, from Rhodobacter capsulatus was previously believed to code for a polypeptide involved in formation of the cyclopentone ring of protochlorophyllide from Mg-protoporphyrin IX monomethyl ester. In this study, R. capsulatus bchM was expressed in Escherichia coli and the gene product was subsequently demonstrated by enzymatic analysis to catalyze methylation of Mg-protoporphyrin IX to form Mg-protoporphyrin IX monomethyl ester. Activity required the substrates Mg-protoporphyrin IX and S-adenosyl-L-methionine. 14C-labeled product was formed in incubations containing 14C-methyl-labeled S-adenosyl-L-methionine. On the basis of these and previous results, we also conclude that the bchH gene, which was previously reported to code for Mg-protoporphyrin IX methyltransferase, is most likely involved in the Mg chelation step.
authors.affiliation: Division of Biology and Medicine, Brown University, Providence, Rhode Island 02912.
authors.forename: D W
authors.initials: DW
authors.lastname: Bollivar
authors.forename: Z Y
authors.initials: ZY
authors.lastname: Jiang
authors.forename: C E
authors.initials: CE
authors.lastname: Bauer
authors.forename: S I
authors.initials: SI
authors.lastname: Beale
mesh_terms: D001429:Bacteriochlorophylls / Q000096:biosynthesis*; D001483:Base Sequence; D002250:Carbon Radioisotopes; D003001:Cloning, Molecular; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli; D015870:Gene Expression; D005798:Genes, Bacterial; D008780:Methyltransferases / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016133:Polymerase Chain Reaction; D011524:Protoporphyrins / Q000378:metabolism; D016354:Rhodobacter capsulatus / Q000201:enzymology* / Q000235:genetics*; D013050:Spectrometry, Fluorescence
chemical_list: D001429:Bacteriochlorophylls; D002250:Carbon Radioisotopes; D017931:DNA Primers; D011524:Protoporphyrins; C028025:protoporphyrin IX; D008780:Methyltransferases; C060234:magnesium-protoporphyrin methyltransferase