Feb 4 Flashcards
Does MAPK need to be PO4’d on both sites to be active?
Yes
What subunits are PO4’d, by what for Phk?
The a and b subunit are PO4’d by PKA, but the Y subunit has Glu, it is a pseudokinase, it is neg glu so it is bound in active confrormation
What does PTEN dephosphorylate?
PIP3, so deactivates the signalling molecule
What sithe PPP family of phosphatases specific for? What is special about it?
It is for Ser and Thr, it is highly conserved between species
What is the PPM phosphatase family? What substrates and what is special about it?
It is ser and thr specific, it is Mg2+ dependent. They are unrelated to PPP family but still have similar active sites, so convergent evolution
What is special about the PTP family? What motif does it have, why work the way it does?
It is phosphatase for tyrosines. It has CX5R motif, so C, then 5 X’s, then R. It has deep pocket with this motif in the bottom, ser and thr side chains aren’t long enough for the PO4 to reach the motif, so specific only for Tyr
What is an example of one of class 1 PTP’s?
They dephosphorylate Tyr residues, they include the dual-specificity family. MAPK is activated by growth factors.
What is the substrate of class 2 PTP’s
Cyclin dependent kinases (CDKs)
Is a PO4’d CDK active or inactive?
It is inactive
Class 3 PTP’s are also known as what?
Low MW PTPs
What do Asp-based phosphatases do? What do substrates have? Example?
The substrates have repeats, an example is CTD of RNA Pol 2.
What toxins do dinoflagellates produce? What about microsystin? What do these toxins do?
Okadaic acid for dinoflagellate, microcystin produces a cyclic heptapeptide. These are both specific toxins for PPP family of phosphatases (PP1, PP2A, PP2B). It targets phosphatases so always PO4’d myosin light chains so contracted muscle does not relax.
What helps regulate PP1 specificity? What is consequence of antigen replacing this thing for MAPK and therefore the cell?
The alpha B subunit controls protein phosphatase 1 (PP1) activity. These regulatory subunits have an RVXF motif that binds in the cleft between the N and C lobes of the phosphatase. If an antigen replaces the B subunit, then the phosphatase has no specificity so MAPK not dePO4’d so grow signal always on?
What does subunit A of Protein phosphatase 2A (PP2A) do? What about B subunit?
It is a scaffold for the B and C subunits. PP2A is trimeric phosphatase. B subunit is needed for substrate specificity
