lHeim_B

Tau20C phosphorylation.

AI Overview (Google's Gemini, March 26, 2026)

Yes, multiple phosphate (PO4) molecules can bind within the same functional regions or "pockets" of the tau protein, particularly in cases of hyperphosphorylation associated with Alzheimer’s disease.

Clustered Phosphorylation Sites: Tau is an intrinsically disordered protein (IDP) with about 85 potential phosphorylation sites. These sites are heavily clustered in the proline-rich region (residues 172-251) and the C-terminal tail (residues 368-441), which flank the microtubule-binding repeats. This high density means multiple phosphate groups often populate these regions simultaneously.
Binding Pocket Overlap: In the pathological, "hyperphosphorylated" state, the balance of kinases and phosphatases is disrupted, leading to the accumulation of many phosphate groups on a single tau molecule.
Specific Examples: Research shows that in Alzheimer’s diseased brains, hyperphosphorylated tau often has 5–9 phosphorylation sites modified, compared to only 2–3 in healthy adults.
Effect of Multiple Phosphates: The binding of multiple phosphates acts cumulatively. As more phosphate groups bind to tau, they remove the positive charge of the microtubule-binding region (MTBR), causing the tau protein to lose its affinity for microtubules, leading to aggregation.
Cooperative Binding: Phosphorylation at one site can sometimes prime or enhance phosphorylation at nearby sites within the same binding domain, facilitating the clustering of multiple phosphates.

In summary, the high concentration of potential sites in specific domains makes it likely that multiple phosphate groups reside in the same or closely positioned areas, directly causing the conformational changes that lead to pathology.

Order of binding	Receptor	Ligand	Affinity	Pocket ID	Residues that formed the binding pocket	Presence of SER, THR, TYR
1	Tau20C	PO4	-2.769	receptor_Tau20C_1	LEU-693 THR-694 PHE-695 ASN-698 ALA-699	THR-694
2	Tau20C	PO4	-2.65	receptor_Tau20C_7	VAL-269 ASP-270 PHE-271 LEU-272 SER-273 LYS-274 VAL-275	SER-273
3	Tau20C	PO4	-2.707	receptor_Tau20C_7	VAL-269 ASP-270 PHE-271 LEU-272 SER-273 LYS-274 VAL-275	SER-273
4	Tau20C	PO4	-2.629	receptor_Tau20C_13	VAL-573 LYS-574 SER-575 GLY-578 THR-580 GLU-581	SER-575 THR-580
5	Tau20C	PO4	-2.516	receptor_Tau20C_7	VAL-269 ASP-270 PHE-271 LEU-272 SER-273 LYS-274 VAL-275	SER-273
6	Tau20C	PO4	-2.514	receptor_Tau20C_11	VAL-667 GLN-668 SER-669 GLY-672 LEU-674 ASP-675	SER-669
7	Tau20C	PO4	-2.455	receptor_Tau20C_10	ILE-734 ASP-735 MET-736 VAL-737 ASP-738 SER-739	SER-739
8	Tau20C	PO4	-2.334	receptor_Tau20C_11	VAL-667 GLN-668 SER-669 GLY-672 LEU-674 ASP-675	SER-669
9	Tau20C	PO4	-2.332	receptor_Tau20C_7	VAL-269 ASP-270 PHE-271 LEU-272 SER-273 LYS-274 VAL-275	SER-273