lHeim_B

Tau13C 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	Tau13C	PO4	-2.594	receptor_Tau13C_8	VAL-680 PRO-681 GLY-682 GLY-683 GLY-684 ASN-685
2	Tau13C	PO4	-2.474	receptor_Tau13C_7	VAL-604 GLN-605 SER-606 GLY-609 SER-610 LYS-611 ASP-612	SER-606 SER-610
3	Tau13C	PO4	-2.205	receptor_Tau13C_7	VAL-604 GLN-605 SER-606 GLY-609 SER-610 LYS-611 ASP-612	SER-606 SER-610
4	Tau13C	PO4	-2.229	receptor_Tau13C_7	VAL-604 GLN-605 SER-606 GLY-609 SER-610 LYS-611 ASP-612	SER-606 SER-610
5	Tau13C	PO4	-2.104	receptor_Tau13C_3	ILE-734 ASP-735 MET-736 VAL-737 ASP-738 SER-739 GLN-741 LEU-742 LEU-745	SER-739
6	Tau13C	PO4	-1.959	receptor_Tau13C_2	ASP-510 ARG-511 SER-512	SER-512
7	Tau13C	PO4	-1.934	receptor_Tau13C_3	ILE-734 ASP-735 MET-736 VAL-737 ASP-738 SER-739 GLN-741 LEU-742 LEU-745	SER-739
8	Tau13C	PO4	-2.437	receptor_Tau13C_3	ILE-734 ASP-735 MET-736 VAL-737 ASP-738 SER-739 GLN-741 LEU-742 LEU-745	SER-739
9	Tau13C	PO4	-2.337	receptor_Tau13C_3	ILE-734 ASP-735 MET-736 VAL-737 ASP-738 SER-739 GLN-741 LEU-742 LEU-745	SER-739