Proline Rich Protein 21 (PRR21)

PRR21 consists of 389 amino acids or 1170 base pairs, all found within one exon. Like other proline-rich proteins, it contains a repeated sequence of amino acids that contains several proline residues. The tandemly repeated sequence of PRR21 is 28 amino acids long and is repeated in full 11 times, with few variations. A logo displaying the variances of the repeat is shown below. The repeat constitute almost the entire protein, except for the very beginning and a short tail. PRR21 has 28 possible phosphorylation sites. These follow the patterns of the repeated sequence. 22 out of 28 phosphorylation sites occur at serines at positions 9 and 24 in the repeat, both of which are highly conserved. Though, these serines can be changed by SNPs. Phosphorylation generally either activates or inactivates a protein.