lHeim_B

Tau25A 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	Tau25A	PO4	-2.778	receptor_Tau25A_10	VAL-604 GLN-605 SER-606 CYS-608 GLY-609 SER-610 LYS-611 ASP-612	SER-606 SER-610
2	Tau25A	PO4	-2.697	receptor_Tau25A_1	LEU-693 THR-694 PHE-695 ASN-698 ALA-699	THR-694
3	Tau25A	PO4	-2.537	receptor_Tau25A_11	LYS-660 LEU-661 ASP-662 ASP-665 ARG-666
4	Tau25A	PO4	-2.458	receptor_Tau25A_10	VAL-604 GLN-605 SER-606 CYS-608 GLY-609 SER-610 LYS-611 ASP-612	SER-606 SER-610
5	Tau25A	PO4	-2.447	receptor_Tau25A_6	ILE-734 ASP-735 MET-736 VAL-737 ASP-738 SER-739 LEU-742	SER-739
6	Tau25A	PO4	-2.4	receptor_Tau25A_10	VAL-604 GLN-605 SER-606 CYS-608 GLY-609 SER-610 LYS-611 ASP-612	SER-606 SER-610
7	Tau25A	PO4	-2.615	receptor_Tau25A_10	VAL-604 GLN-605 SER-606 CYS-608 GLY-609 SER-610 LYS-611 ASP-612	SER-606 SER-610
8	Tau25A	PO4	-2.378	receptor_Tau25A_6	ILE-734 ASP-735 MET-736 VAL-737 ASP-738 SER-739 LEU-742	SER-739
9	Tau25A	PO4	-2.364	receptor_Tau25A_14	LYS-692 LEU-693 THR-694 PHE-695 ARG-696 GLU-697 HIS-724 SER-726	THR-694 SER-726