The effects of supplementing specific amino acids on the expression of elastin-like polypeptides (ELPs)

Elastin-like polypeptides (ELPs) made from the repeating pentapeptides (Val-Pro-Gly-Xaa-Gly) are protein based biopolymers that contain useful properties, including the ability to self-assemble, biocompatibility, and stimuli sensitivity. However, due to the repeated consumption of specific amino acids, long ELPs generally have low expression yields in in vitro and in vivo systems. This is because of the lack of specific amino acids during the translation process. In this study, ELP fusion proteins of various lengths were prepared by recursive directional ligation (RDL) and expressed in a cell-free protein synthesis system. By measuring TCA-precipitated radioactivity with a liquid scintillation counter, their expression profiles were investigated. The expression levels of an ELP fusion protein were improved by almost 2-fold by adding specific amino acids. Additionally, we determined that the amount of increase in expression levels depends on the length of the ELPs. This study suggests a useful strategy to improve the yield of longer repetitive polypeptides such as ELPs or silk-like polypeptides (SLPs).