Proteinase B Disruption Is Required for High Level Production of Human Mechano-Growth Factor in Saccharomyces cerevisiae

Mechano-growth factor (MGF) is a product of a unique muscle-specific splice variant of the insulin-like growth factor I gene. Potential use of MGF to improve regenerative capability of skeletal muscle as well as to prevent neuronal damage has been widely discussed. Human MGF was expressed in Saccharomyces cerevisiae, but the yield of the recombinant protein was low due to its rapid degradation. The proteinase B was identified as the enzyme responsible for MGF processing. A yeast strain with Δprb1 deletion was created resulting in a fivefold increase of MGF yield that reached 50 mg/l. The biological activity of recombinant MGF was verified in a proliferation assay employing human postnatal myoblasts.