E) Representative western blot of the solubility analysis of GK variants upon overexpression in E. coli K12. Bands show Soluble (Sol) and Pellet fractions after centrifugation at 17,100 g for 15 mins. "-DnaK" indicates expression in E. coli K12 DnaK knockout line, "+ Dnak" indicates co-expression of pKJE7, encoding DnaK, DnaJ and GrpE. 