Anti-MAP2K1 (phospho S221) Antibody

Raised in rabbit against a synthetic phosphopeptide corresponding to the activation-loop sequence surrounding serine 221 of human MEK1, this affinity-purified polyclonal IgG selectively recognises MAP2K1 only when phosphorylated at Ser221. The unconjugated reagent is supplied as 50 µl of polyclonal serum in PBS (pH 7.3) with 50% glycerol and 0.02% sodium azide, and Antibodies.com validates its use across Western blot, immunohistochemistry, and immunofluorescence workflows on Human, Mouse, and Rat samples.

Ser221 lies in subdomain VIII of the MEK1 activation loop and is phosphorylated by upstream RAF kinases, so this reagent is routinely used to monitor flux through the canonical RAS-RAF-MEK-ERK cascade. Researchers apply it to characterise pathway activation in BRAF- or KRAS-driven tumour models, to follow phosphorylation kinetics after growth-factor, serum, or stress stimulation, and to map activation state in fixed or frozen rodent tissue. Non-phospho-specific antibodies are removed during antigen-affinity purification over the immunising phosphopeptide, and storage at -20 °C in working aliquots is recommended to preserve phospho-specific binding through repeated freeze-thaw cycles.