- D. W. Lim and K. Trabbic-carlson and J. A. Mackay and A. Chilkoti, Improved non-chromatographic purification of a recombinant protein by cationic elastin-like polypeptides,
Biomacromolecules, vol. 8 no. 5
pp. 1417 -- 1424 .
(last updated on 2009/09/02)
This paper reports an improvement in the purification of thioredoxin (Trx) expressed from E. coli by inverse transition cycling (ITC) using cationic elastin-like polypeptides (ELPs). Two ELP libraries having 2\% and 5\% lysine residues and molecular weights ranging from 4 to 61.1 kDa showed greater salt sensitivity in their inverse transition behavior than purely aliphatic ELPs. Expression yield of Trx-ELP fusions was an unpredictable function of guest residue composition, but reducing the molecular weight of the ELP tag generally increased Trx yield. A cationic 4.3 kDa ELP is the shortest ELP used to purify any protein by ITC to date. A 15.9 kDa ELP with a guest residue composition of K:V:F of 1:7:1 was found to be the optimal cationic tag to purify Trx, as it provided 50\% greater Trx yield and only required one-fifth the added NaCl for purification of Trx as compared to previously used aliphatic ELP tags.