Is E37, a major polypeptide of the inner membrane from plastid envelope, an S-adenosyl methionine-dependent methyltransferase?

Plant J. 1996 Nov;10(5):903-12. doi: 10.1046/j.1365-313x.1996.10050903.x.

Abstract

Using antibodies raised against E37, one of the major polypeptides of the inner membrane from the chloroplast envelope, it has been demonstrated that a single immunologically related polypeptide was present in total protein extracts from various higher plants (monocots and dicots), in photosynthetic and non-photosynthetic tissues from young spinach plantlets, as well as in the cytoplasmic membrane from the cyanobacteria Synechococcus. This ubiquitous distribution of E37 strongly suggests that this protein plays an envelope-specific function common to all types of plastids. Comparison of tobacco and spinach E37 amino acid sequences deduced from the corresponding cDNA demonstrates that consensus motifs for S-adenosyl methionine-dependent methyltransferases are located in both sequences. This hypothesis was confirmed using a biochemical approach. It was demonstrated that E37, together with two minor spinach chloroplast envelope polypeptides of 32 and 39 kDa, can be specifically photolabeled with [3H]-S-adenosyl methionine upon UV-irradiation. Identification of E37 as a photolabeled polypeptide was established by immunoprecipitation. Furthermore, photolabeling of the three envelope polypeptides was specifically inhibited by very low concentration of S-adenosyl homocysteine, thus providing evidence for the presence within these proteins of S-adenosyl methionine- and S-adenosyl homocysteine-binding sites that were closely associated. Taken as a whole these results strongly suggest that E37 is an ubiquitous plastid envelope protein that probably has an S-adenosyl methionine-dependent methyltransferase activity. The 32 and 39 kDa envelope polypeptides probably have a similar methyltransferase activity.

MeSH terms

  • Amino Acid Sequence
  • Blotting, Western
  • Chloroplast Proteins
  • Methyltransferases / chemistry*
  • Molecular Sequence Data
  • Plant Proteins / chemistry*
  • Plastids / chemistry*
  • Sequence Alignment

Substances

  • Chloroplast Proteins
  • Plant Proteins
  • Methyltransferases
  • methionine S-methyltransferase

Associated data

  • GENBANK/L20427
  • GENBANK/M98330
  • GENBANK/X56963
  • GENBANK/X94968