Division in synthetic cells.

The bottom-up construction of a living cell using non-living materials represents a grand challenge in science and technology. Reproduction of cells into similar offspring is key to life, and therefore, building a synthetic cell that can autonomously divide is one of the most fundamental tasks that need to be achieved in bottom-up synthetic biology. In this review, we summarize the strategies of inducing synthetic division by using physical, chemical, and biological stimuli, and highlight the future challenges to the construction of autonomous synthetic cell division.

Structural Basis for the Magnesium-Dependent Activation and Hexamerization of the Lon AAA+ Protease.

The Lon AAA+ protease (LonA) plays important roles in protein homeostasis and regulation of diverse biological processes. LonA behaves as a homomeric hexamer in the presence of magnesium (Mg(2+)) and performs ATP-dependent proteolysis. However, it is also found that LonA can carry out Mg(2+)-dependent degradation of unfolded protein substrate in an ATP-independent manner. Here we show that in the presence of Mg(2+) LonA forms a non-secluded hexameric barrel with prominent openings, which explains why Mg(2+)-activated LonA can operate as a diffusion-based chambered protease to degrade unstructured protein and peptide substrates efficiently in the absence of ATP. A 1.85 Å crystal structure of Mg(2+)-activated protease domain reveals Mg(2+)-dependent remodeling of a substrate-binding loop and a potential metal-binding site near the Ser-Lys catalytic dyad, supported by biophysical binding assays and molecular dynamics simulations. Together, these findings reveal the specific roles of Mg(2+) in the molecular assembly and activation of LonA.