The extrinsic proteins of photosystem II of higher plants and green algae PsbO, PsbP, PsbQ, and PsbR are essential for stable oxygen production in the oxygen evolving center. In the available X-ray crystallographic structure of higher plant PsbQ residues S14-Y33 are missing. Building on the backbone NMR assignment of PsbQ, which includes this "missing link", we report the extended resonance assignment including side chain atoms. Based on nuclear Overhauser effect spectra a high resolution solution structure of PsbQ with a backbone RMSD of 0.81 Å was obtained from torsion angle dynamics. Within the N-terminal residues 1-45 the solution structure deviates significantly from the X-ray crystallographic one, while the four-helix bundle core found previously is confirmed. A short α-helix is observed in the solution structure at the location where a β-strand had been proposed in the earlier crystallographic study. NMR relaxation data and unrestrained molecular dynamics simulations corroborate that the N-terminal region behaves as a flexible tail with a persistent short local helical secondary structure, while no indications of forming a β-strand are found.

• Keywords
• Spinacia oleracea, dynamic N-terminus, extrinsic photosynthetic protein, hydrogen bond dynamics, intrinsic disorder, solution structure,
• MeSH
• Photosystem II Protein Complex chemistry   genetics   metabolism   MeSH
• Crystallography, X-Ray MeSH
• Magnetic Resonance Spectroscopy methods   MeSH
• Recombinant Proteins chemistry   metabolism   MeSH
• Plant Proteins chemistry   genetics   metabolism   MeSH
• Solutions MeSH
• Protein Structure, Secondary * MeSH
• Amino Acid Sequence MeSH
• Molecular Dynamics Simulation * MeSH
• Spinacia oleracea genetics   metabolism   MeSH
• Protein Structure, Tertiary MeSH
• Thermodynamics MeSH
• Protein Binding MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Photosystem II Protein Complex MeSH
• Recombinant Proteins MeSH
• Plant Proteins MeSH
• Solutions MeSH