Molecular cloning, expression and purification of lactoferrin from Tibetan sheep mammary gland using a yeast expression system

• A lactoferrin (LF) gene from Tibetan sheep was expressed in a yeast host.
• The yield of recombinant LF was >60 mg L−1 with specific activity 2533.33 U mg−1.
• Recombinant LF shows potential as a human antibiotic, as it inhibited bacterial growth.

This paper reports the successful expression of a lactoferrin gene—obtained from the mammary gland tissue of Tibetan sheep—in the yeast Pichia pastoris GS115 using pPICZαA as the recombinant plasmid and α-factor signal sequence for secretion. The recombinant lactoferrin was purified by ammonium sulfate precipitation, ion-exchange column chromatography and gel-filtration chromatography, and it had a molecular mass of 76 kDa. We obtained an expression yield of >60 mg L−1 and specific activity of 2533.33 U mg−1. The antimicrobial activities and iron-binding behaviors of recombinant lactoferrin indicated that it was correctly folded and functional. Additionally, recombinant lactoferrin inhibited the growth of Escherichia coli JM109 and Staphylococcus aureus. These findings indicate that recombinant lactoferrin is a potential antibiotic for use on humans. This study also demonstrates the successful expression of recombinant lactoferrin using the eukaryotic host organism P. pastoris, paving the way for protein engineering using this gene.