Search for: All records

Life is far from thermodynamic equilibrium. Hence, life must extract energy from the environment. On Earth, that energy is driven by networks of metabolic reactions in all cells which ultimately move electrons and protons (i.e. hydrogen atoms) across the planet. The origin of metabolism required the emergence and evolution of proteins. Proteins are nanometre-scale chemical machines—i.e. literal nanomachines which physically move. These nanomachines enable living systems to perform essential biochemical tasks from replication to metabolism; the latter being the engines of life. In all extant life on Earth, a small set of these nanomachines, called oxidoreductases, couple chemical energy from the environment with core redox reactions including photosynthesis, respiration and nitrogen fixation. The origins and emergence of complex life have been intimately tied with evolution of oxidoreductases. Here, using structure-based analyses, we describe the evolution of the protein catalysts in three biological epochs. First, thermodynamically driven polymerization reactions generated simple metal-binding peptides with specific sequences that catalysed core metabolic reactions. Second, these catalysts were incorporated in small structural ‘folds’. In the third epoch, these folds served as building blocks for extant, complex nanomachines. This article is part of the discussion meeting issue ‘Chance and purpose in the evolution of biospheres’. 

Nucleoside triphosphate (NTP)-dependent protein assemblies such as microtubules and actin filaments have inspired the development of diverse chemically fueled molecular machines and active materials but their functional sophistication has yet to be matched by design. Given this challenge, we asked whether it is possible to transform a natural adenosine 5′-triphosphate (ATP)-dependent enzyme into a dissipative self-assembling system, thereby altering the structural and functional mode in which chemical energy is used. Here we report that FtsH (filamentous temperature-sensitive protease H), a hexameric ATPase involved in membrane protein degradation, can be readily engineered to form one-dimensional helical nanotubes. FtsH nanotubes require constant energy input to maintain their integrity and degrade over time with the concomitant hydrolysis of ATP, analogous to natural NTP-dependent cytoskeletal assemblies. Yet, in contrast to natural dissipative systems, ATP hydrolysis is catalyzed by free FtsH protomers and FtsH nanotubes serve to conserve ATP, leading to transient assemblies whose lifetimes can be tuned from days to minutes through the inclusion of external ATPases in solution. 

In this report, we explore the internal structural features of polyMOFs consisting of equal mass ratios of metal-coordinating poly(benzenedicarboxylic acid) blocks and non-coordinating poly(ethylene glycol) (PEG) blocks. The studies reveal alternating lamellae of metal-rich, crystalline regions and metal-deficient non-crystalline polymer, which span the length of hundreds of nanometers. Polymers consisting of random PEG blocks, PEG end-blocks, or non-coordinating poly(cyclooctadiene) (COD) show similar alternation of metal-rich and metal-deficient regions, indicating a universal self-assembly mechanism. A variety of techniques were employed to interrogate the internal structure of the polyMOFs, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and small-angle synchrotron X-ray scattering (SAXS). Independent of the copolymer architecture or composition, the internal structure of the polyMOF crystals showed similar lamellar self-assembly at single-nanometer length scales.