As Chien (pronounced Chen) explains, to carry out fundamental life processes such as growing and dividing, cells must orchestrate, in time and location, the production and degradation of hundreds of protein substrates. Even in simple bacteria, protein degradation is critical for making sure these organisms can grow and respond to their environment properly.
Caulobacter crescentus (above) generates radically different cell types upon division. The ClpXP protease (illustrated below) recognizes and destroys many protein substrates that allow Caulobacter to differentiate into these different cell types. New work identifying scores of new candidate substrates of ClpXP to reveal how protein degradation is critical to cell cycle progression and bacterial development could lead to new antibiotic targets.
Scientists have known that a group of protein machines called energy-dependent proteases are responsible for the majority of this degradation, but what targets these machines recognize and how they do it has been unknown in many cases.
With the new series of experiments in the model bacteria Caulobacter crescentus in the Chien biochemistry and molecular biology laboratory, much more is now understood, he says. “We first generated a protease mutant that could recognize but not destroy its targets, acting as a ‘trap’ for protease substrates. After purifying this trap from living cells, we used mass spectrometry to identify proteins that were caught, finding over a hundred new candidate substrates. These targets covered all aspects of bacterial growth, including DNA replication, transcription and cytoskeletal changes.”
The work was funded by a grant from the National Institute of General Medical Sciences at the National Institutes of Health and by UMass Amherst.
Peter Chien | Newswise
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