Table 2 Properties of the proteins selected as expression reporters

Luciferase

reporter protein, ~ 60.8 kDa, cytoplasmic localization, generally low expression, rather easy to detect, very sensitive detection via bioluminescence assay

scFv173-2-5-AP

industrially relevant protein, ~77.2 kDa, fusion protein, disulfide bonds, translocated to the periplasm, detectable through AP^a fusion, AP needs to be translocated to be active [34]

GFP

reporter protein, ~ 26.9 kDa, cytoplasmic localization, stable, known to be produced virtually only in its soluble form [35], very easy to detect by direct fluorometry

HGH

industrially relevant protein, ~25.1 kDa, cytoplasmic localization, usually expressed in E. coli as soluble protein [36, 37]

IL-1RA

industrially relevant protein, ~20.1 kDa, cytoplasmic localization, usually expressed in E. coli as soluble protein [38, 39]