Abstract
The structure of the unusually long (~100 amino-acid residues) N-terminal domain of the light-harvesting protein CP29 of plants is not defined in the crystal structure of this membrane protein. We studied the N-terminus using two electron paramagnetic resonance (EPR) approaches: the rotational diffusion of spin labels at 55 residues with continuous-wave EPR, and three sets of distances with a pulsed EPR method. The N-terminus is relatively structured. Five regions that differ considerably in their dynamics are identified. Two regions have low rotational diffusion, one of which shows a-helical character suggesting contact with the protein surface. This immobile part is flanked by two highly dynamic, unstructured regions (loops) that cover residues 10-22 and 82-91. These loops may be important for the interaction with other light-harvesting proteins. The region around residue 4 also has low rotational diffusion, presumably because it attaches noncovalently to the protein. This section is close to a phosphorylation site (Thr-6) in related proteins, such as those encoded by the Lhcb4.2 gene. Phosphorylation might influence the interaction with other antenna complexes, thereby regulating the supramolecular organization in the thylakoid membrane.
Original language | English |
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Pages (from-to) | 1349-1358 |
Journal | Biophysical Journal |
Volume | 106 |
Issue number | 6 |
DOIs | |
Publication status | Published - 2014 |
Keywords
- light-harvesting complex
- electron-paramagnetic-resonance
- comprehensive software package
- labeled side-chains
- photosystem-ii
- distance measurements
- conformational-changes
- structure prediction
- energy-transfer
- t4 lysozyme