Heterologous expression of the bchM gene product from Rhodobacter capsulatus and demonstration that it encodes S-adenosyl-L-methionine:Mg-protoporphyrin IX methyltransferase

J Bacteriol. 1994 Sep;176(17):5290-6. doi: 10.1128/jb.176.17.5290-5296.1994.

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.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacteriochlorophylls / biosynthesis*
  • Base Sequence
  • Carbon Radioisotopes
  • Cloning, Molecular
  • DNA Primers
  • Electrophoresis, Polyacrylamide Gel
  • Escherichia coli
  • Gene Expression*
  • Genes, Bacterial*
  • Methyltransferases / biosynthesis*
  • Methyltransferases / genetics
  • Methyltransferases / isolation & purification
  • Molecular Sequence Data
  • Molecular Weight
  • Polymerase Chain Reaction
  • Protoporphyrins / metabolism
  • Rhodobacter capsulatus / enzymology*
  • Rhodobacter capsulatus / genetics*
  • Spectrometry, Fluorescence

Substances

  • Bacteriochlorophylls
  • Carbon Radioisotopes
  • DNA Primers
  • Protoporphyrins
  • protoporphyrin IX
  • Methyltransferases
  • magnesium-protoporphyrin methyltransferase