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MK-STYX

A

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B

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Phosphorylation catalysis.  (A) Protein tyrosine phosphatase (PTP) cleaves the phosphate from the tyrosine residue of a phosphorylated protein. (B) The pseudophosphatase binds the phosphorylated residue, but doesn't cleave the phosphate because of essential residues missing from its active motif (HCX5R).

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Active PTP         HCX5R

MK-STYX      FSX5R

 

Schematic representation of MK-STYX. MK-STYX has dual specificity (DSP) and CH2  (cdc 25 homology) domains. An active DSP domain would dephosphorylate phosphoserine/threonine/tyrosine residues.  MK-STYX is catalytically inactive due to the absence of two amino acids within in the DSP domain that are essential for phosphatase activity. However, MK-STYX has the ability to bind phosphorylated proteins. The CH2 domain, also known as the Rhodanese domain, binds mitogen activated kinases in MK-STYX active homologs.