Recombinant human HPK1 (also known as MAP4K1, Mitogen-activated protein kinase kinase kinase kinase 1), encompassing amino acids 1-346 containing the kinase domain of the protein. In this construct the N-terminal end is fused with GST, linked to the protein via a short peptide linker corresponding to a thrombin cleavage site. The construct also contains a C-terminal His tag (6xHis) followed by an Avi-Tag™. The protein was affinity purified.