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Project Progress

A new project was begun to probe the evolution of novel enzyme activities by recruitment of pre-existing proteins. While enzymes are generally highly evolved to perform certain functions, they often have adventitious secondary activities as a consequence of the assemblage of highly reactive groups in their active sites. If these secondary activities become useful to the organism, the enzyme can be recruited to perform a new function. Subsequent mutations can then lead to improvements in that new function. This process has been profoundly important in the evolution of living organisms, providing the basis for the evolution of novel metabolic pathways that have allowed organisms to take advantage of the wide range of environmental niches available on Earth.

We have designed a new experimental system to address a fundamentally important question: from how many sources can a protein be recruited to provide a function critical for life? Some insight into this question can be gained from analysis of known proteins, but the existing repertoire of proteins reflects what did happen, rather than what could have happened. In order to define what could have happened, we plan to knock out genes required for survival in E. coli, and then introduce a plasmid-based library containing all of the genes in E. coli and ask which genes can restore viability, even at a very low level, by providing a protein that can be recruited to fill the missing function. During this first year we generated the plasmid-based library, developed the methods for recovering slow-growing strains that have recruited a new enzyme, and began to create strains in which several critical genes have been knocked out.