[Protein budget: cost estimating criteria for synthetic biology]

The aim of synthetic biology is to design artificial life systems. Such system is hoped to create a better production process with desired ability for bioproduction, biotransformation, adaption and environmental monitoring. However, to design a life system involves understanding the cellular regulation networks at multiple levels, in which the controls of protein level, subcelluar location, and activity are especially critical. Thus tuning protein expression has become essential tools in synthetic biology studies, such as part design, module assembly and compatibility optimization. Protein budget, just like budget for a factory, can be thought as the cost estimating criteria for an artificial cell factory. Protein budget control has provided a powerful optimization strategy for synthetic biology.