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Light-oxygen-voltage (LOV) domains are increasingly used to engineer photoresponsive biological systems. While the photochemical cycle is well documented, the allosteric mechanism by which formation of a cysteinyl-flavin adduct leads to activation is unclear. Via replacement of flavin mononucleotide (FMN) with 5-deazaflavin mononucleotide (5dFMN) in the Aureochrome1a (Au1a) transcription factor from Ochromonas danica, a thermally stable cysteinyl-5dFMN adduct was generated. High-resolution crystal structures (<2 Å) under different illumination conditions with either FMN or 5dFMN chromophores reveal three conformations of the highly conserved glutamine 293. An allosteric hydrogen bond network linking the chromophore via Gln293 to the auxiliary A′α helix is observed. With FMN, a “flip” of the Gln293 side chain occurs between dark and lit states. 5dFMN cannot hydrogen bond through the C5 position and proved to be unable to support Au1a domain dimerization. Under blue light, the Gln293 side chain instead “swings” away in a conformation distal to the chromophore and not previously observed in existing LOV domain structures. Together, the multiple side chain conformations of Gln293 and functional analysis of 5dFMN provide new insight into the structural requirements for LOV domain activation.

This review article covers recent developments in the use of enzymecatalyzed reactions to control molecular selfassembly SA, an area that merges the advantages of biocatalysis with soft materials selfassembly. This approach is attractive because it combines biological chemo, regio, and enantio selectivity with the versatility of bottom up nanofabrication through dynamic SA. We define enzymeassisted SA eSA as the production of molecular building blocks from nonassembling precursors via enzymatic catalysis, where molecular building blocks form ordered structures via noncovalent interactions. The molecular design of SA precursors is discussed in terms of three key components related to i enzyme recognition, ii molecular switching mechanisms, and iii supramolecular interactions that underpin SA. This is followed by a discussion of a number of unique features of these systems, including spatiotemporal control of nucleation and structure growth, the possibility of controlling mechanical properties and the defect correcting and component selecting capabilities of systems that operate under thermodynamic control. Applications in biomedicine biosensing, controlled release, matrices for wound healing, controlling cell fate by gelation and bionanotechnology biocatalysts immobilization, nanofabrication, templating, and intracellular imaging are discussed. Overall, eSA allows for unprecedented control over SA processes and provides a step forward toward production of nanostructures of higher complexity and with fewer defects as desired for next generation nanomaterials. © 2010 Wiley Periodicals, Inc. Biopolymers Pept Sci 94:107–117, 2010.This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymerswiley.com

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