Human MLK1, also known as Mixed Lineage Kinase 1, Mitogen-activated protein kinase kinase kinase 9, MAP3K9, MEKK9, and PRKE1, GenBank Accession No. NM_033141, a.a. 1-433, with N-terminal GST-tag, MW = 77 kDa, expressed in Sf9 cells via a baculovirus expression system.