Anti-CTNNB1 (phospho S33) Antibody

This rabbit polyclonal IgG reagent from Antibodies.com is raised against human CTNNB1 phosphorylated at serine 33 and is supplied as 100 µl of unconjugated antibody. It is validated for western blot detection of the S33-phosphorylated form of β-catenin, a key regulatory modification within the canonical Wnt signaling pathway.

Serine 33 sits within the N-terminal regulatory region of β-catenin (approximately 85 kDa) and is phosphorylated by GSK-3β within the multiprotein destruction complex containing APC, Axin, and casein kinase 1. Together with the adjacent phospho-Ser37 and Thr41 sites, modification at Ser33 generates the phosphodegron recognized by the E3 ubiquitin ligase adaptor β-TrCP, priming β-catenin for proteasomal turnover. Detecting this specific phospho-form in human cell lysates therefore reports directly on destruction-complex activity and on pathway inhibition following Wnt ligand stimulation, small-molecule GSK-3 inhibition, or comparative analysis of cancer-associated signaling mutants.

The unconjugated polyclonal format from Antibodies.com gives researchers flexibility to pair the antibody with their preferred HRP- or fluorophore-conjugated secondary detection reagent, and the polyclonal response provides tolerance for minor variation around the phospho-S33 epitope. For clean western blot interpretation, lysates should be prepared with fresh phosphatase inhibitors to preserve the S33 modification, and signals should be normalized against total CTNNB1 alongside a standard loading control so that changes in phosphorylation can be distinguished from changes in overall β-catenin abundance.