Production of a 135-residue long N-truncated human keratinocyte growth factor 1 in Escherichia coli

Abstract

Background: Palifermin (trade name Kepivance®) is an amino-terminally truncated recombinant human keratinocyte growth factor 1 (KGF-1) with 140 residues that has been produced using Escherichia coli to prevent and treat oral mucositis following radiation or chemotherapy. In this study, an amino-terminally shortened KGF-1 variant with 135 residues was produced and purified in E. coli, and its cell proliferation activity was evaluated. Results: We expressed soluble KGF-1 fused to thioredoxin (TRX) in the cytoplasmic fraction of E. coli to improve its production yield. However, three N-truncated forms (KGF-1 with 140, 138, and 135 residues) were observed after the removal of the TRX protein from the fusion form by cleavage of the human enterokinase light chain C112S (hEKL C112S). The shortest KGF-1 variant, with 135 residues, was expressed by fusion with TRX via the hEKL cleavage site in E. coli and purified at high purity (> 99%). Circular dichroism spectroscopy shows that purified KGF-1135 had a structure similar to that of the KGF-1140 as a random coiled form, and MCF-7 cell proliferation assays demonstrate its biological activity. Conclusions: We identified variations in N-terminus-truncated KGF-1 and selected the most stable form. Furthermore, by a simple two-step purification, highly purified KGF-1135 was obtained that showed biological activity. These results demonstrate that KGF-1135 may be considered an alternative protein to KGF-1.