High-resolution solution structure of reduced parsley plastocyanin

Area of Science:

• Biochemistry
• Structural Biology
• Plant Science

Background:

• Plastocyanin is a copper-containing protein involved in electron transfer in photosynthesis.
• Previous structural studies of plastocyanins have utilized X-ray diffraction and NMR methods.

Purpose of the Study:

• To determine the high-resolution three-dimensional solution structure of parsley plastocyanin.
• To investigate the structural basis for interactions with cytochrome f.

Main Methods:

• High-resolution 3D structure determination using 1H-NMR-derived data.
• Calculation of an ensemble of 30 conformers to represent structural variability.

Main Results:

• The global fold of parsley plastocyanin is similar to other characterized plastocyanins.
• Deletion of residues 57-58 eliminates a turn in the acidic binding site.
• Substitutions at positions 59-60 further alter the acidic recognition site.
• Residues E53, E85, and E95 compensate for substitutions, maintaining a similar acidic site extent.

Conclusions:

• Parsley plastocyanin possesses a unique acidic binding site due to residue deletions and substitutions.
• Despite alterations, the binding site maintains a similar acidic character to other higher plant plastocyanins.
• The structural findings provide insights into the interaction mechanism with cytochrome f.