Full-Length Recombinant Human SCF(1-165) Is More Thermostable than the Truncated SCF(1-141) Form

Human stem cell factor initiates a diverse array of cellular responses, including hematopoiesis, cell proliferation, differentiation, migration and survival. To explore the relationship between its structure and function, we produced recombinant soluble human stem cell factor(1–165) (wild type) and human stem cell factor(1–141) (C-terminal truncated) in a yeast expression system and compared their biological activities and thermal stabilities. The biological activity of the two proteins was measured as a function of TF-1 cell viability and effects on downstream signaling targets after incubation. We found that these proteins enhanced cell viability and downstream signaling to a similar extent, in a dose-dependent manner. The biological activity of recombinant human stem cell factor(1–165) was significantly greater than that of recombinant human stem cell factor(1–141) after heating the proteins (100 ng/mL) at 25–110°C for 10 minutes (P<0.05 for all temperatures). In addition, circular dichroism spectral analysis indicated that β-sheet structures were altered in recombinant human stem cell factor(1–141) but not recombinant human stem cell factor(1–165) after heating at 90°C for 15 or 30 min. Molecular modeling and limited proteolytic digestion were also used to compare the thermo stability between human stem cell factor(1–165) and human stem cell factor(1–141). Together, these data indicate that stem cell factor(1–165) is more thermostable than stem cell factor(1–141).