Distinct 'assisted' and 'spontaneous' mechanisms for the insertion of polytopic chlorophyll-binding proteins into the thylakoid membrane

Soo Jung Kim, Stefan Jansson, Neil E. Hoffman, Colin Robinson, Alexandra Mant

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

The biogenesis of several bacterial polytopic membrane proteins has been shown to require signal recognition particle (SRP) and protein transport machinery, and one such protein, the major light-harvesting chlorophyll- binding protein (LHCP) exhibits these requirements in chloroplasts. In this report we have used in vitro insertion assays to analyze four additional members of the chlorophyll-a/b-binding protein family. We show that two members, Lhca1 and Lhcb5, display an absolute requirement for stroma, nucleoside triphosphates, and protein transport apparatus, indicating an 'assisted' pathway that probably resembles that of LHCP. Two other members, however, namely an early light-inducible protein 2 (Elip2) and photosystem II subunit S (PsbS), can insert efficiently in the complete absence of SRP, SecA activity, nucleoside triphosphates, or a functional Sec system. The data suggest a possibly spontaneous insertion mechanism that, to date, has been characterized only for simple single-span proteins. Of the membrane proteins whose insertion into thylakoids has been analyzed, five have now been shown to insert by a SRP/Sec-independent mechanism, suggesting that this is a mainstream form of targeting pathway. We also show that PsbS and Elip2 molecules are capable of following either 'unassisted' or assisted pathways, and we discuss the implications for the mechanism and role of SRP in chloroplasts.

Original languageEnglish (US)
Pages (from-to)4715-4721
Number of pages7
JournalJournal of Biological Chemistry
Volume274
Issue number8
DOIs
StatePublished - Feb 19 1999
Externally publishedYes

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Signal Recognition Particle
Chlorophyll Binding Proteins
Thylakoids
Light-Harvesting Protein Complexes
Membranes
Chloroplasts
Membrane Proteins
Proteins
Nucleoside Transport Proteins
Nucleosides
Photosystem II Protein Complex
Protein Transport
Light
Machinery
Assays
Molecules

ASJC Scopus subject areas

  • Biochemistry

Cite this

Distinct 'assisted' and 'spontaneous' mechanisms for the insertion of polytopic chlorophyll-binding proteins into the thylakoid membrane. / Kim, Soo Jung; Jansson, Stefan; Hoffman, Neil E.; Robinson, Colin; Mant, Alexandra.

In: Journal of Biological Chemistry, Vol. 274, No. 8, 19.02.1999, p. 4715-4721.

Research output: Contribution to journalArticle

Kim, Soo Jung ; Jansson, Stefan ; Hoffman, Neil E. ; Robinson, Colin ; Mant, Alexandra. / Distinct 'assisted' and 'spontaneous' mechanisms for the insertion of polytopic chlorophyll-binding proteins into the thylakoid membrane. In: Journal of Biological Chemistry. 1999 ; Vol. 274, No. 8. pp. 4715-4721.
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