Transglutaminase-mediated assembly of multi-enzyme pathway onto TMV brush surfaces for synthesis of bacterial autoinducer-2

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Bioelectronic microdevices, with spatially arranged biosynthetic machinery, can be programmed to convert raw materials to high-value products in a controlled manner. Generic methods for biofunctionalization that enable precise control over biocomponent assembly at the nano and meso scales are necessary to diversify the range and capabilities of these systems. Here, we used tobacco mosaic virus (TMV) derived virus like particles (VLPs) as 3D interfacial scaffolds for the assembly of biosynthetic enzymes onto gold electrodes. The TMV capsids are aligned in a vertical brush configuration by cysteine modifications to the capsid protein and by taking advantage of the well-known gold/cysteine affinity. This alignment enables high surface density and biosynthetic enzyme-enzyme proximity. Enzymes are covalently tethered to the capsid protein of TMV by the N- and C-terminal addition of lysine-rich assembly domains which react with surface exposed glutamine residues on the capsid surfaces; the lysine/glutamine linkages are mediated by a microbial transglutaminase (mTG). We demonstrate flexible mTG-mediated assembly of a three-enzyme biosynthetic pathway that converts S-adenosylmethionine (SAM) to autoinducer-2 (AI-2), a bacterial signal molecule that mediates quorum sensing behavior. We propose that our VLP and mTG based fabrication approach will help in the modular assembly of biological components onto microelectronic devices and that these will find utility in many applications including sensing and lab on chip devices.