Phospho-PDK1 (Ser241) refers to the protein PDK1 that is phosphorylated at the Ser241 site. PDK1, full name 3-phosphoinositide-dependent protein kinase-1, is a serine/threonine protein kinase that plays a central role in regulating cell growth, survival, and proliferation. Overexpression of PDK1 in cells has been observed in breast and ovarian cancers, and its activity increases in prion-infected neurons. Phosphorylation of a conserved serine (S241) in the activation loop leads to the activation of PDK1.