A team of UC San Francisco scientists, in work published in the March 14 issue of Science, have shown how a toolkit of modular molecular components and circuit boards can be used to engineer a wide variety of biochemical circuits in living cells, much as the old Heathkit electronic kits of the 1950s enabled students and hobbyists to assemble modular electronic parts into working radios and computers. The work is part of the growing field of synthetic biology, in which scientists are trying to learn how to engineer cells to help solve medical, industrial, and environmental problems. Supported by grants from DARPA, the NIH, and the University of California, the work was carried out in UCSF's Department of Cellular and Molecular Pharmacology and in the California Institute of Quantitative Biosciences (QB3) by graduate student Caleb Bashor, lead author on the work, postdoctoral fellows Noah Helman and Shude Yan, and Professor Wendell Lim, senior author on the work. Lim is a participant in the Synthetic Biology Engineering Research Center (SynBERC), an NSF-funded center headquartered at UC Berkeley that also involves researchers at UCSF, MIT, Harvard, and Prairie View A&M University. Many of the behaviors of living cells are determined by circuits composed of proteins known as kinases, which are found in organisms ranging from yeasts to plants to humans. These proteins can transmit information via a molecular signal known as phosphorylation. Kinase circuits can determine how a cell will respond to signals in its environment, and are used to control cell growth, differentiation, and immune response. Precisely how kinase molecules are wired together determines how a cell will respond. In many cases, specific kinase components are wired together in a specific arrangement by molecules known as scaffolds. These scaffolds operate essentially as molecular circuit boards, analogous to the circuit boards from electronic kits in that they bind and organize the wiring between individual molecular components.