Structural basis for the modular recognition of single-stranded RNA by PPR proteins

Area of Science:

• Molecular Biology
• Structural Biology
• Plant Science

Background:

• Pentatricopeptide repeat (PPR) proteins are crucial for RNA metabolism in plants.
• PPR proteins recognize single-stranded RNA (ssRNA) modularly, particularly in plant organelles.
• The maize chloroplast protein PPR10 binds specific RNA elements, defining mRNA termini.

Purpose of the Study:

• To elucidate the structural basis of sequence-specific ssRNA recognition by PPR proteins.
• To determine the crystal structures of the maize PPR10 protein in both RNA-free and RNA-bound states.

Main Methods:

• X-ray crystallography was used to obtain structures of PPR10.
• Structures were determined at 2.85 Å (RNA-free) and 2.45 Å (RNA-bound) resolution.
• The binding of PPR10 to an 18-nucleotide PSAJ RNA element was analyzed.

Main Results:

• The RNA-free PPR10 structure shows nineteen repeats forming a right-handed superhelical spiral.
• PPR10 forms an antiparallel, intertwined homodimer.
• Upon binding an 18-nucleotide PSAJ RNA element, PPR10 undergoes conformational changes, with six repeats specifically recognizing six RNA bases (A, G, U).

Conclusions:

• The study reveals the molecular basis for specific and modular recognition of RNA bases by PPR proteins.
• The structural insights into PPR10-RNA interaction provide a framework for biotechnological applications in RNA research.