Photosynthesis Research

, Volume 50, Issue 1, pp 41–59

Characterization of the csmD and csmE genes from Chlorobium tepidum. The CsmA, CsmC, CsmD, and CsmE proteins are components of the chlorosome envelope

  • Soohee Chung
  • Donald A. Bryant
Regular Paper

DOI: 10.1007/BF00018220

Cite this article as:
Chung, S. & Bryant, D.A. Photosynth Res (1996) 50: 41. doi:10.1007/BF00018220

Abstract

The csmD and csmE genes, encoding two proteins of the chlorosome envelope, have been cloned and sequenced from the green sulfur bacterium Chlorobium tepidum. The csmD gene predicts a hydrophobic protein of 113 amino acids with a molecular mass of 11.1 kDa. The csmE gene was identified immediately upstream from csmD; the csmE gene predicts a protein of 82 amino acids (9.0 kDa) which is 49% identical to CsmA (Chung et al. (1994) Photosynthesis Res 41: 261–275). The CsmE protein is post-translationally processed, most likely in a manner similar to CsmA. The csmE and csmD genes are cotranscribed as a dicistronic mRNA but can also be cotranscribed with an open reading frame upstream from csmE that predicts a protein with sequence similarity to the CheY and SpoOF subclass of regulatory proteins. The CsmA, CsmC, CsmD, and CsmE proteins were overproduced in Escherichia coli, purified, and used to raise polyclonal antibodies in rabbits. Protease susceptibility mapping and agglutination experiments using these antibodies indicate that all four proteins are exposed at the surface of isolated chlorosomes and hence are probably components of the chlorosome envelope. Additionally, antigalactose antibodies were used to confirm that the galactosyl moiety of monogalactosyl diglycerol is exposed at the chlorosome surface; this is consistent with the notion that these lipids are components of the chlorosome envelope.

Key words

green sulfur bacteriumChlorobium tepidumchlorosomesDNA sequenceprotein overproductionprimer extension mappinglight-harvesting antennaphotosynthesis

Abbreviations

BChl-

bacteriochlorophyll

bp-

basepair(s)

C.-

Chloroflexus

Cb.-

Chlorobium

Csm-

chlorosome protein

csm

gene encoding a chlorosome protein

IPTG

isopropyl-β-d-thiogalatoside

nt

nucleotide

ORF

open reading frame

PAGE

polyacrylamide gel electrophoresis

SDS

sodium dodecylsulfate

Copyright information

© Kluwer Academic Publishers 1996

Authors and Affiliations

  • Soohee Chung
    • 1
    • 2
  • Donald A. Bryant
    • 1
    • 2
  1. 1.Department of Biochemistry and Molecular BiologyThe Pennsylvania State UniversityUniversity Park
  2. 2.Center for Biological Structure and FunctionThe Pennsylvania State UniversityUniversity Park
  3. 3.Department of Molecular and Cellular BiologyHarvard UniversityCambridge