Cloning and sequencing of cDNA encoding bovine macrophage colony-stimulating factor (bM-CSF) and expression of recombinant bM-CSF using baculovirus

The cDNAs encoding bovine macrophage colony-stimulating factors α and β (M-CSFα and M-CSFβ) were cloned and recombinant bovine M-CSFα (rbM-CSFβ) in its dimeric form was expressed by using a recombinant baculovirus/insect cell system. The predicted amino acid sequence of rbM-CSFα and rbM-CSFβ shared 83.3 and 75.9% (α), 75.3 and 65.9% (β) similarity with the sequence for human and murine M-CSFs, respectively. The biological activity of rbM-CSFβ was confirmed by the colony-forming assay using mouse bone marrow cells. SDS-PAGE under a reducing condition showed that the molecular weight of rbM-CSFβ was approximately 34 kDa. On the other hand, Western blot analysis under a non-reducing condition revealed that this rbM-CSFβ was secreted in dimeric form into the cell supernatant.