Phosphatase Family FCP

Phosphatase Classification: Fold HAD: Superfamily HAD: Family FCP

FCP contains five catalytically active subfamilies, and one inactive one (TIMM50). Four of the five catalytically active subfamilies act on the C-terminal domain (CTD) of RNA polymerase II (Pol II). The CTD consists of tandem repeated heptapeptide segments of a consensus YSPTSPS sequence, and the different phosphorylation patterns that predominate at each stage of transcription recruit the appropriate set of mRNA-processing and histone-modifying factors. FCP1 and SCP have different preference over pSer2 and pSer5. See Phosphorylation of RNA polymerase II C-terminal domain.

FCP1

F-cell production 1 (FCP1) also called TFIIF-stimulated CTD phosphatase 1, prefers to dephosphorylate pSer2 of the CTD

SCP

SCP is named after Small CTD (carboxy-terminal domain, RNA polymerase II, polypeptide A) phosphatase. This subfamily has three members in human, SCP1 (or CTDSP1), SCP2 (or CTDSP2), and SCP3 (or CTDSPL). SCP1 prefers to dephosphorylate pSer5.

Dullard

Dullard, is also known as CTDNEP1 (CTD nuclear envelope phosphatase 1). However, its known substrate is lipin rather than RNA polymerase II CTD. The kinase of yeast lipin, SMP2, is Cdc28/cdk1.

CTDSPL2

A poorly-described but almost pan-eukaryotic CTD phosphatase.

UBLCP1

UBLCP1 is named after Ubiquitin-like domain containing CTD phosphatase 1. It has not been well characterized. It has a N-terminal domain similar to ubiquitin. Its putative substrate is the CTD.

TIMM50

TIMM50, translocase of inner mitochondrial membrane 50 homolog. Catalytically inactive.

DxDxT motif

The pattern of DxDxT motif are obtained from eight organisms, yeast, Monosiga, sponge, anemone, worm, fly, sea urchin, and human.

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Subfamily	Motif pattern	Note
FCP1	DLDQT
SCP	DLDET
Dullard	DLDET	Exceptionally, one of the three fly Dullards has DMDNT.
HSPC129	DLDET
UBLCP1	D[I|V]DYT
TIMM50	-	Not very conserved.