Table 1 The synthetic biology toolbox: common components used in synthetic biological systems

Transcriptional

Constitutive promoter libraries [19, 20]

Provide continuously ON gene expression at pre-determined levels

Inducible promoters (for example, responsive to tetracycline, IPTG, gaseous acetaldehyde [22], or light [23])

Provide conditional and, in certain cases, titratable gene expression in response to inducer signal

Posttranscriptional

Non-coding regulatory RNAs [28] (such as riboregulators [29, 30], ribozyme switches [31, 51], and RNAi switches [32, 33])

Control protein production levels by regulating mRNA stability or translation initiation in response to molecular input

Alternative splicing modulators [35]

Control protein production levels or protein activity by regulating alternative splicing of mRNA in response to molecular input

RNase substrate libraries [80]

Control protein levels through tunable hairpin elements that direct transcript cleavage

Posttranslational

Degradation tags [24, 25]

Modulate protein levels by shortening protein half-lives

Split inteins [26, 27]

Provide biosensing and modulate protein activity by conditionally splicing inactive protein fragments together into functional wholes

Structural

Protein [36–39], RNA [40], and DNA [93] scaffolds

Regulate signaling and metabolic pathway flux by controlling the localization and stoichiometry of pathway components and intermediate products