|PROSITE documentation PDOC50275 [for PROSITE entry PS50275]|
The Sac domain is a region of homology between the N-terminus of synaptojanin and the otherwise unrelated yeast protein Sac1p. The Sac domain is approximately 400 residues in length, and proteins containing this domain show approximately 35% identity with other Sac domains throughout this region. The Sac domain exhibits phosphatidylinositol polyphosphate phosphatase activity and can hydrolyse phosphate from any of the three positions of inositol that may be phosphorylated (3-, 4- and 5). However, adjacent phosphates are resistant to hydrolysis. Sac domains cannot hydrolyse phosphate from phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P2), or PtdIns(3,4)P2, or PtdIns(3,4,5)P3, but can hydrolyse PtdIns(3,5)P2 [1,2].
The Sac domain consists of seven highly conserved motifs which appear to define the catalytic and regulatory regions of the phosphatase. The sixth conserved region contains a highly conserved C-x(5)-R-[TS] motif, thought to be the catalytic motif of many metal-independent protein and inositide polyphosphate phosphatases. Interestingly, the Inp51p Sac domain in which the cysteine, arginine and threonine/serine residues within the C-x(5)-R-[TS] motif are absent, does not exhibit any phosphatase activity [1,2].
Two classes of Sac domain proteins have been identified in mammals as well as lower eukaryotes [1,2]. The first comprises proteins, which, in addition to an N-terminal phosphatase Sac domain, have all the domains associated with type II phosphatidylinositol phosphate 5-phosphatases:
The other class of Sac-containing phosphatases consists of proteins with an N-terminal Sac phosphatase domain and no other recognizable domains:
The profile we developed covers the seven highly conserved motifs found in Sac domains.Last update:
January 2002 / First entry.
PROSITE method (with tools and information) covered by this documentation:
|Title||The Sac phosphatase domain.|
|Source||Curr. Biol. 11:R249-R249(2001).|
|2||Authors||Hughes W.E. Cooke F.T. Parker P.J.|
|Source||Biochem. J. 350 Pt 2:337-352(2000).|