Abstract
The light-harvesting chlorophyll a/b binding proteins (LHCP) belong to a large family of membrane proteins. They form the antenna complexes of photosystem I and II and function in light absorption and transfer of the excitation energy to the photosystems. As nuclear-encoded proteins, the LHCPs are imported into the chloroplast and further targeted to their final destination—the thylakoid membrane. Due to their hydrophobicity, the formation of the so-called ‘transit complex’ in the stroma is important to prevent their aggregation in this aqueous environment. The posttranslational LHCP targeting mechanism is well regulated through the interaction of various soluble and membrane-associated protein components and includes several steps: the binding of the LHCP to the heterodimeric cpSRP43/cpSRP54 complex to form the soluble transit complex; the docking of the transit complex to the SRP receptor cpFtsY and the Alb3 translocase at the membrane followed by the release and integration of the LHCP into the thylakoid membrane in a GTP-dependent manner. This review summarizes the molecular mechanisms and dynamics behind the posttranslational LHCP targeting to the thylakoid membrane of Arabidopsis thaliana.
Highlights
Introduction and overview oflight-harvesting chlorophyll a/b binding proteins (LHCP) transport to the thylakoid membraneThe capture of light energy is essential for biomass production through photosynthesis
We summarize the molecular details of the individual steps of posttranslational cpSRP-dependent LHCP transport in plants, including cpSRP43/cpSRP54 heterodimerization, cpSRP/LHCP transit complex formation, docking of the transit complex at the thylakoid membrane, and insertion of LHCP into the membrane
The release of LHCP from cpSRP is triggered upon interaction of cpSRP43 with the insertase Alb3, as it was shown that the addition of recombinant Alb3 C-terminus dissociates soluble cpSRP43/LHCP complexes (Lewis et al 2010; Liang et al 2016) and that this effect is coupled to the presence of the cpSRP43 binding motifs II and IV in Alb3 C-terminus (Liang et al 2016)
Summary
Introduction and overview ofLHCP transport to the thylakoid membraneThe capture of light energy is essential for biomass production through photosynthesis. Keywords LHCP · CpSRP · Transit complex · Alb3 · CpFtsY · Thylakoid membrane
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