FIRRM binds PPP1CC

The C-terminus of FIRRM (also known as Apolo1 or FLIP or C1orf112) contains a canonical PP1 docking motif KVVSF and binds to PP1gamma (PPP1CC), inhibiting PPP1CC-mediated dephosphorylation of the PLK1 threonine residue T210. The phosphorylation of the RV[S/T]F motifs is a general mechanism for negative control of the interaction of PP1 with its regulatory proteins. The serine residue S744 in the KVVSF motif of FIRRM is highly conserved among different vertebrate species, but overall is the least conserved residue of the KVVSF motif. Phosphorylation of FIRRM at S744 by PLK1 negatively regulates FIRRM binding to PPP1CC (Xu et al. 2021).

FIRRM（亦称Apolo1、FLIP或C1orf112）的C端含有经典的PP1结合位点KVVSF，并与PP1gamma（PPP1CC）结合，从而抑制PPP1CC介导的PLK1苏氨酸残基T210的去磷酸化。RV[S/T]F基序的磷酸化是负向调控PP1与其调节蛋白相互作用的普遍机制。在FIRRM的KVVSF基序中，丝氨酸残基S744在不同脊椎动物物种中高度保守，但总体而言，它是KVVSF基序中最不保守的残基。PLK1对S744的磷酸化负向调控FIRRM与PPP1CC的结合（Xu等人，2021年）。