title: The N-terminal domain of Lhcb proteins is critical for recognition of the LHCII kinase.
abstract: The light-harvesting chlorophyll (Chl) a/b complex of photosystem (PS) II (LHCII) plays important roles in the distribution of the excitation energy between the two PSs in the thylakoid membrane during state transitions. In this process, LHCII, homo- or heterotrimers composed of Lhcb1-3, migrate between PSII and PSI depending on the phosphorylation status of Lhcb1 and Lhcb2. We have studied the mechanisms of the substrate recognition of a thylakoid threonine kinase using reconstituted site-directed trimeric Lhcb protein-pigment complex mutants. Mutants lacking the positively charged residues R/K upstream of phosphorylation site (Thr) in the N-terminal domain of Lhcb1 were no longer phosphorylated. Besides, the length of the peptide upstream of the phosphorylated site (Thr) is also crucial for Lhcb phosphorylation in vitro. Furthermore, the two N-terminal residues of Lhcb appear to play a key role in the phosphorylation kinetics because Lhcb with N-terminal RR was phosphorylated much faster than with RK. Therefore, we conclude that the substrate recognition of the LHCII kinase is determined to a large extent by the N-terminal sequence of the Lhcb proteins. The study provides new insights into the interactions of the Lhcb proteins with the LHCII kinase.
authors.affiliation: Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Wu
authors.initials: W
authors.lastname: Liu
authors.affiliation: Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
authors.forename: Wenfeng
authors.initials: W
authors.lastname: Tu
authors.affiliation: Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
authors.forename: Ruixue
authors.initials: R
authors.lastname: Sun
authors.affiliation: Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Liu
authors.affiliation: Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China. Electronic address: yangch@ibcas.ac.cn.
authors.forename: Chunhong
authors.initials: C
authors.lastname: Yang
mesh_terms: D000595:Amino Acid Sequence; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000502:physiology*; D016825:Chlamydomonas reinhardtii / Q000201:enzymology; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology*; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D013379:Substrate Specificity
chemical_list: D029681:Arabidopsis Proteins; C423618:CAB2 protein, Arabidopsis; C000602509:Lhcb2 protein, Arabidopsis; D045342:Light-Harvesting Protein Complexes; D011494:Protein Kinases; C120337:light-harvesting complex II kinase
keywords: Kinase; Light harvesting complex; N-terminal; Protein interactions