title: Light-harvesting complex II protein CP29 binds to photosystem I of Chlamydomonas reinhardtii under State 2 conditions.
abstract: The State 1 to State 2 transition in the photosynthetic membranes of plants and green algae involves the functional coupling of phosphorylated light-harvesting complexes of photosystem II (LHCII) to photosystem I (PSI). We present evidence suggesting that in Chlamydomonas reinhardtii this coupling may be aided by a hyper-phosphorylated form of the LHCII-like CP29 protein (Lhcbm4). MS analysis of CP29 showed that Thr6, Thr16 and Thr32, and Ser102 are phosphorylated in State 2, whereas in State 1-exposed cells only phosphorylation of Thr6 and Thr32 could be detected. The LHCI-PSI supercomplex isolated from the alga in State 2 was found to contain strongly associated CP29 in phosphorylated form. Electron microscopy suggests that the binding site for this highly phosphorylated CP29 is close to the PsaH protein. It is therefore postulated that redox-dependent multiple phosphorylation of CP29 in green algae is an integral part of the State transition process in which the structural changes of CP29, induced by reversible phosphorylation, determine the affinity of LHCII for either of the two photosystems.
authors.affiliation: Wolfson Laboratories, Division of Molecular Biosciences, Imperial College London, UK.
authors.forename: Joanna
authors.initials: J
authors.lastname: Kargul
authors.forename: Maria V
authors.initials: MV
authors.lastname: Turkina
authors.forename: Jon
authors.initials: J
authors.lastname: Nield
authors.forename: Sam
authors.initials: S
authors.lastname: Benson
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Vener
authors.forename: James
authors.initials: J
authors.lastname: Barber
mesh_terms: D000818:Animals; D001665:Binding Sites; D016825:Chlamydomonas reinhardtii / Q000737:chemistry*; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry / Q000378:metabolism*; D013058:Mass Spectrometry; D008854:Microscopy, Electron; D046912:Multiprotein Complexes / Q000737:chemistry; D010084:Oxidation-Reduction; D010766:Phosphorylation; D045331:Photosystem I Protein Complex / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding
chemical_list: C069660:CP29 light harvesting complex; D045342:Light-Harvesting Protein Complexes; D046912:Multiprotein Complexes; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex