A comparative analysis of the properties of regulated promoter systems commonly used for recombinant gene expression in Escherichia coli

Table 3 Summary of the findings derived from the comparative expression study

Category	Regulator/promoter system				References
	XylS/Pm and Pm ML1-17	LacI/P_T7lac	LacI/P_trc	AraC/P_BAD
Components	XylS regulator	LacI regulator	LacI regulator	AraC regulator
	Pm promoter (native or variant)	T7lac promoter	trp/lac hybrid promoter	P_BAD promoter
		CAP binding site		CAP binding site
Strain requirements	none	strain supplying T7 polymerase	none	araBADC-/ araEFGH+ strain
		(and lysozyme)^a
Medium requirements	none	(glucose)^b	none	(glucose)^b	[3, 10, 11, 42]
Range of inducer	0.001 - 2.0 mM	0.05 - 2.0 mM	0.05 - 2.0 mM	0.001% - 1%	[1, 25]
Expression level	low - high	intermediate - high	low - intermediate	intermediate - high	This study
Basal expression	low - high	low - high	High	low	This study
Induction ratio	intermediate	intermediate-high	Low	high	This study
Accumulated transcript	low - intermediate	high	below detection - intermediate	intermediate	This study
RBS strength	weak - intermediate	intermediate - strong	weak - intermediate	strong	This study
Homogeneity	homogeneous populations	mixed populations	homogeneous populations	mixed populations	This study
Recommended applications	high level expression	high level expression	(high level expression)^c	high level expression
	expression of toxic proteins	(expression of toxic proteins)^c	(metabolic engineering)^c	expression of toxic proteins
	metabolic engineering			(metabolic engineering)^c	This study

^a Expression of lysozyme, the natural inhibitor of T7 RNA polymerase, reduces the basal transcription from P_T7lac.
^b Supplementing glucose leads to catabolite repression which reduces basal transcription levels.
^c Limited suitability. See ‘Results and discussion’ section for detailed information.

ISSN: 1475-2859