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Danja Schnemann
Mechanisms of protein import into thylakoids of chloroplasts
Keywords: chloroplast, protein transport, Sec, SRP, TAT, thylakoid membrane
The thylakoid membrane of chloroplasts contains the major photosynthetic complexes, which consist of several either nuclear- or chloroplast-encoded subunits. The biogenesis of these thylakoid membrane complexes requires the coordinated transport and subsequent assembly of the subunits into functional complexes. Nuclear-encoded thylakoid proteins are first imported into the chloroplast and then directed to the thylakoid by using different sorting mechanisms. The cpSec-pathway and the cpTat-pathway are mainly involved in the transport of lumenal proteins, whereas the spontaneous-pathway and the cpSRP-pathway are used for the insertion of integral membrane proteins into the thylakoid membrane. While cpSec-, cpTat- and cpSRPmediated targeting can be classified as 'assisted' mechanisms involving numerous components, the ‘unassisted' spontaneous insertion does not require additional targeting factors. However, even the assisted pathways differ fundamentally with respect to stromal targeting factors, the composition of the translocase and energy requirements.
Biological Chemistry, Walter de Gruyter
Print ISSN: 1431-6730
Volume: 2007
Pages: -