Seminar: Designing biology to move cargo across membranes

Today, Danielle Tullman-Ercek from University of California, Berkeley is presenting “Getting through the gatekeepers: Changing the selectivity of semi-permeable cellular membranes.”

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At a broad level, Danielle is fascinated by the transformational potential of synthetic biology. She thinks a lot about how the organization of living cells and biologically produced materials can be engineered to impact things like bioproduction and even architecture (plants engineered to grow into shapes for houses and other buildings, glowing tress to provide light at night, etc.).

Specifically, she focuses on the the cell membrane, an excellent naturally occurring example of how a material can be engineered to do extremely useful things such as filter impurities, conduct signals, and compartmentalize biochemical reactions. Natural cell membranes are fatty ‘bubbles’ that separate contents from aqueous environments. The fatty membrane is studded with large protein complexes that act as gatekeepers that allow molecules to pass into and out of the bubble.

The antibiotic efflux pump is one such gatekeeper. It has the remarkable ability to force toxic antibiotics out of the cell, even when the concentration difference dictates that toxin should be flowing into the cell. Danielle’s group engineered new versions of this pump by using directed evolution. Their new pumps are designed to help bioengineered cells to sustain butanol production. Current systems allow butanol to build up inside the cell, which is toxic. The engineered pump allows the cells to pump out the desired product as the cell continues to produce it.

Danielle’s group has also made progress towards engineering entire synthetic compartments (similar to organelles) inside of bacteria. Compartmentalization is important for separating different biochemical reactions inside the cell, as well as storing compounds that might be toxic if they are allowed to diffuse freely in the cell.

Here work will open new avenues toward custom-built control of processes within commercially important microbes that produce valuable compounds and chemicals.

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