Toehold Switches
Biopolymers · 2014
Synthetic biology has succeeded in developing novel gene networks for the construction of biological devices. However, underlying problems in synthetic biology remain the limited number of composable, arise when integrating multiple components into a large, complex synthetic network. Indeed, biological components often interact with one another in the cellular environment and suffer from unwanted crosstalk between components. Limitations imposed by the number and orthogonality of available biological circuit components hinder the construction of more complex circuits that can operate robustly in living cells. In this article, Green et al. report a class of de-novo-designed prokaryotic ribo-regulators termed toehold switches that activate gene expression in response to cognate RNAs with arbitrary sequences. The authors show that the switches can be integrated into the genome to regulate endogenous genes and use them as sensors that respond to endogenous RNAs. Toehold switches, with their wide dynamic range, orthogonality, and programmability, may represent a versatile platform for regulation of translation, offering diverse applications in molecular biology and biotechnology. Green, A. G. et al. Cell, 159, 1–15 (2014). The rotary motor enzyme F1-ATPase (F1) is a catalytic subcomplex of FoF1-ATP synthase that produces ATP in respiring cells. Chemomechanical coupling has been studied extensively for bacterial F1 yet little is know about mitochondrial F1. In this paper, the authors characterize ATP-driven rotation of human mitochondrial F1. The rotor-shaft γ-subunit in the stator α3β3 ring rotates 120° per ATP with three catalytic steps: ATP binding to one β-subunit at 0°, inorganic phosphate release from another β-subunit at 65° and ATP hydrolysis on the third β-subunit at 90°. Rotation is often interrupted at 90° by persistent ADP binding and is stalled at 65° by a specific inhibitor azide. A mitochondrial endogenous inhibitor for of FoF1-ATP synthase, IF1, blocks rotation at 90°. These features differ from those of bacterial F1, in which both ATP hydrolysis and Pi release occur at around 80°. Thus, chemomechanical coupling of human mitochondrial F1 differs from that of bacterial F1 suggesting that the coupling angles of the γ-subunit are tuned during evolution to optimize the synthesis of ATP Suzuki, T. et al. Nat. Chem. Biol., Published online 21 September 2014.