An Arabidopsis thaliana cDNA encoding PS II-X, a 4.1 kDa component of photosystem II: A bipartite presequence mediates SecA/ΔpH-independent targeting into thylakoids

Soo Jung Kim, David Robinson, Colin Robinson

Research output: Contribution to journalArticle

28 Scopus citations

Abstract

Higher plant photosystem II preparations contain a 4.1 kDa polypeptide (subunit X) associated with the oxygen-evolving core complex. We describe the isolation of a cDNA encoding PS II-X from Arabidopsis thaliana, in which the C-terminal region is highly homologous to partially sequenced PS II-X from wheat and spinach. The mature protein of 42 residues is preceded by a 74-residue, bipartite presequence similar to those involved in the targeting of nuclear-encoded thylakoid lumen proteins, although hydrophobicity analysis indicates the presence of a single transmembrane span in the mature protein. Moreover, import of pre-PS II-X into the thylakoid membrane of isolated chloroplasts is unaffected by inhibitors of either the Sec- or ΔpH-dependent thylakoidal protein translocases, suggesting a spontaneous insertion mechanism. PS II-X appears to be encoded as a mature protein by the plastid genome in the chlorophyll a+c-containing alga, Odontella sinensis. We thus propose that the thylakoid transfer signal of Arabidopsis pre-PS II-X represents a recent acquisition, in phylogenetic terms, compared with signals of Sec-dependent lumenal proteins.

Original languageEnglish (US)
Pages (from-to)175-178
Number of pages4
JournalFEBS Letters
Volume390
Issue number2
DOIs
StatePublished - Jul 22 1996

Keywords

  • Chloroplast
  • Photosynthesis
  • Photosystem II
  • Protein translocation
  • Thylakoid
  • psbX

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology
  • Genetics
  • Cell Biology

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