Enables kinase binding activity and protein serine/threonine kinase activator activity. Involved in intracellular signal transduction; peptidyl-serine phosphorylation; and positive regulation of protein phosphorylation. Located in extracellular exosome. Implicated in hepatocellular carcinoma. Biomarker of hepatocellular carcinoma and pancreatic cancer. [provided by Alliance of Genome Resources, Apr 2022]