Protein Phosphatase 1, Regulatory Subunit 1A (PPP1R1A)

PPP1R1A deduced 171-amino acid protein has a calculated molecular mass of 19.2 kD. I1 shares over 85% identity with rabbit and rat I1, with 97% identity in the first 58 residues. Recombinant human I1 had an apparent molecular mass of 28 kD by SDS-PAGE.I1-alpha lacks 1 exon and encodes a deduced 120-amino acid protein with an in-frame 51-amino acid deletion following the N-terminal inhibitor domain of full-length I1. I1-beta lacks 2 exons and encodes a deduced 132-amino acid protein identical to I1 and I1-alpha over the first 61 amino acids, but with a unique C-terminal region due to a frameshift. Both isoforms retain the protein phosphatase-1 (PP1)-binding motif between residues 8 and 12 (RKIQF) and the critical phosphorylation site at thr35.