Abstract
The most abundant chlorophyll-binding complex in plants is the intrinsic membrane protein light-harvesting complex II (LHC II). LHC II acts as a light-harvesting antenna and has an important role in the distribution of absorbed energy between the two photosystems of photosynthesis. We used spectroscopic techniques to study a synthetic peptide with identical sequence to the LHC IIb N terminus found in pea, with and without the phosphorylated Thr at the 5th amino acid residue, and to study both forms of the native full-length protein. Our results show that the N terminus of LHC II changes structure upon phosphorylation and that the structural change resembles that of rabbit glycogen phosphorylase, one of the few phosphoproteins where both phosphorylated and non-phosphorylated structures have been solved. Our results indicate that phosphorylation of membrane proteins may regulate their function through structural protein-protein interactions in surface-exposed domains.
Highlights
Light harvesting complex II (LHC II)1 is a major chlorophyllcontaining protein complex that accounts alone for half of the pigments involved in photosynthesis in plants
To see whether a structural change occurs within the N-terminal domain itself, we have studied a synthetic peptide with the N-terminal sequence normally found in pea [9] with and without the phosphorylation site at position 5 (Thr)-5 synthetically phosphorylated
circular dichroism (CD), nuclear magnetic resonance (NMR), and Fourier transform infrared (FTIR) Spectroscopy of LHC II Peptides—All three spectroscopic methods revealed distinct differences between the non-phosphorylated and phosphorylated forms of a 15-residue peptide corresponding to the N-terminal phosphorylation site of LHC II
Summary
Light harvesting complex II (LHC II) is a major chlorophyllcontaining protein complex that accounts alone for half of the pigments involved in photosynthesis in plants. Tron crystallography of 2-dimensional crystals, a structure for the major part of non-phosphorylated LHC II has been described at 3.4-Å resolution [8] This structure reveals no information regarding the N-terminal domain that contains the phosphorylation site at position 5 (Thr); the protein backbone was traced only to residue 26 where it ends up close to the lipid membrane, consistent with the fact that the sequence between residues 21 and 29 (RVKYLGPF) [9] consists mainly of hydrophobic, aromatic, or charged amino acids. LHC II has been shown to lose its ability to trimerize when more than the first 15 amino acids are removed from the apoprotein [14] At this site, specific lipid-protein interactions between the amino side chains and the lipid phosphatidylglycerol are involved in stabilization of the trimers [15], which implies that only the first 15 amino acid residues at the N terminus may be free of competing interactions with the membrane. Specific changes in structuredependent protein-protein as well as lipid-protein interactions must be the basis of the mechanism by which phosphorylation controls the functional interactions of LHC II in vivo
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
