Sandbox WWC7

Pentatricopeptide repeat (PPR) proteins are a family of sequence specific RNA-binding proteins which participate in organelle RNA metabolism. Although the mechanisms of RNA binding and the functions of PPR proteins are not fully understood, PPR proteins are thought to assist in RNA editing,^[1] translation,^[2] and organelle biogenesis.^[3] They make up the majority of RNA-binding factors in plant organelles. PPR proteins are characterized by a series of tandem-repeat amino acid consensus sequences which form α-helix . These hairpin structures accumulate to form a α-solenoid tertiary structure. PPR proteins belong to one of two classes: P-class and PLS-class, with the P-class containing 35 amino acid repeats and the PLS-class containing 31-36 amino acid repeats. PPR10 is a well-characterized P-class PPR protein found in the chloroplast of Zea mays.^[2]

Function

In the Zea mays plastid, PPR10 binds specifically to the ssRNA oligonucleotides ATPH (17 nucleotides: 5'-GUAUUCUUUAAUUAUUUC-3') and SPAJ (18 nucleotides: 5'-GUAUUCUUUAAUUAUUUC-3') where it has been shown to shield the transcripts from ribonucleases. In addition to stabilizing these RNA sequences, PPR10 increases the rate at which they are translated.^[2]

Mechanism

The primary factor in the ability of PPR10 to bind ATPH and SPAJ in a modular fashion lies in the hydrogen bonding of an AA residue at position 5 of each repeat with a specific base. For example, in the structure to the right, Though van der Waals interactions, Val210 and Arg175 (both orange) also contribute to the specific binding of guanine by forcing it into a conformation where it forms a hydrogen bond to Thr178

Synthetic Applications

There is potential. . .

References