Expression, purification, and crystallization of recombinant human ABL-1 kinase for X-ray crystallography

Abelson-1 (ABL-1) is a nonreceptor tyrosine kinase that plays essential roles in various cellular processes, including proliferation, survival, differentiation and its kinase activity is tightly regulated. The dysregulated ABL-1 kinase activity is linked to disease pathogenesis like Chronic Myeloid Leukemia (CML), where the BCR::ABL-1 fusion oncoprotein drives oncogenic signaling. Due to its central role in CML pathogenesis, understanding the structure of ABL-1 is crucial for the effective management of the disease and drug development studies. This study focuses on optimizing the expression, purification and crystallization of the recombinant human ABL-1 kinase domain for its structural analysis via X-ray crystallography and structure-based drug screening applications. The human ABL-1 kinase domain, fused with a SUMO-tag, was expressed in <i>Escherichia coli</i> Rosetta2 BL21 using the pET28(a)+ expression vector. The ABL-1 aggregates seen under native culture conditions were successfully solubilized by the mild ionic detergent sarkosyl. After obtaining soluble expression of the protein, Ni-NTA affinity chromatography was performed and high yield of purified ABL-1 was obtained. The 6X-His-SUMO-tag of purified ABL1 was cleaved by ULP1 protease. The recombinant ABL-1 was subsequently used in crystallization trials to enlighten structural features of ABL-1 that could guide the development of novel therapeutics and drug screening platforms targeting ABL-1 in CML.