Expression and Purification of Hydrophobic PEP‐Inhibiting Peptides from Bovine αS1 Casein

Abstract

According to previous studies, there is a prolyl endopeptidase‐inhibiting sequence (LNENLLRFFVAPFPEVFG) within a relatively hydrophobic region of αS1 casein (Juillerat‐Jeanneret et al., 2011). Recently, sixteen recombinant peptides were designed in assorted lengths, each containing the inhibitory sequence at varied positions within the αS1 casein sequence. The corresponding cDNA sequences were originally ligated into the pET15b vector, which provides an N‐terminal poly‐histidine tag for purification. The vector was in turn transformed into a BL21(DE3)pLysS E. coli expression host (Vishram et al., 2016). However, the system proved unsuccessful in adequate expression of the hydrophobic peptide. The intention of this study was to assemble a new pET28a expression system, kindly provided by Dr. X. Cheng (MD Anderson in Houston, TX) that utilizes a SUMO (small ubiquitin‐like modifier) fusion tag. The SUMO tag is known for enhancing expression levels of potentially toxic or insoluble recombinant peptides (Bommarius et al., 2010). The expressed peptides were purified via Ni‐NTA column chromatography, with subsequent UlpI cleavage. This was followed by reversed‐phase high performance liquid chromatography (RP‐HPLC) to further purify the peptides. Tricine‐SDS‐PAGE, a useful screening tool for hydrophobic peptides smaller than 30kDa, was used to analyze expression and purification. A comparison was made between SUMO‐fused expression and non‐fused expression of the hydrophobic casein peptides.Support or Funding InformationOffice of Research and Sponsored Projects, SFASU and Ed & Gwen ColeThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.