In mythology, a chimera is a monster composed of distinct parts from several animals. The word "chimera" also has several meanings in biology, based on the mythical concept.

From Dungeons and Drawings, which, as you can see, is pretty great.

Biological chimeras include whole organisms consisting of at least two genetically distinct cells (you might be one), or proteins that consist of two or more proteins (or bits of proteins) fused together. Combining bits of protein is fairly common in synthetic biology. Last year's iGEM team fused whole fluorescent proteins with bits of other proteins responsible for transporting those other proteins to various parts of the cell. The chimeric protein glowed like a fluorescent protein, but, since it included another protein's "I want to be in the nucleus" tag, would be transported to the nucleus.

To create a biosensor, we're attempting the following:

(1) Take an enzyme that can turn a colorless chemical into a colorful signal, and split it in two. Only when the two halves are combined will the enzyme function.


(2) Take each half of the enzyme, and chimerize it with an interacting protein domain. These are interacting domains that want to stick together, but only if a certain signal is present. If there's no signal, then the half-enzymes float around and don't do anything. If the signal is present, the interactive domains stick together, and the half-enzymes are brought into close proximity, and regain (some of) their function.

From Shekhawat and Ghosh in 2012.

That's the plan, at least. We didn't want to put all of our research eggs in one basket, so we've been pursuing these biosensors along with the indigo dye production project. In both cases, we're making dye - either as a colorful response to something, via our biosensors, or for industrial production. The projects sound very different from one another, but draw upon a lot of the same biological and chemical knowledge.


As the summer draws to a close, we're approaching a decision point - which of these research directions do we want to focus on going forward?

Terry D. Johnson is a Berkeley bioengineering lecturer and author. He has been co-advising Berkeley's iGEM team since 2008, and will be one of the lead judges for the North America region this year. His writings here do not necessarily reflect the views of iGEM HQ, Berkeley, or possibly himself, after further contemplation.