Proton-conducting materials play a central role in many renewable energy and bioelectronics technologies, including fuel cells, batteries and sensors. Thus, much research effort has been expended to develop improved proton-conducting materials, such as ceramic oxides, solid acids, polymers and metal-organic frameworks. Within this context, bulk proton conductors from naturally occurring proteins have received somewhat less attention than other materials, which is surprising given the potential modularity, tunability and processability of protein-based materials. Here, we report proton conductivity for thin films composed of reflectin, a cephalopod structural protein. Bulk reflectin has a proton conductivity of ~2.6 × 10(-3) S cm(-1) at 65 °C, a proton transport activation energy of ~0.2 eV and a proton mobility of ~7 × 10(-3) cm(2) V(-1) s(-1). These figures of merit are similar to those reported for state-of-the-art artificial proton conductors and make it possible to use reflectin in protein-based protonic transistors. Our findings may hold implications for the next generation of biocompatible proton-conducting materials and protonic devices.

In nature, cephalopods employ unique dynamic camouflage mechanisms. Herein, we draw inspiration from self‐assembled structures found in cephalopods to fabricate tunable biomimetic camouflage coatings. The reflectance of these coatings is dynamically modulated between the visible and infrared regions of the electromagnetic spectrum in situ. Our studies represent a crucial step towards reconfigurable and disposable infrared camouflage for stealth applications.

Background: synGAP inactivates Ras and Rap at synapses. Results: Phosphorylation of synGAP by CaMKII increases Rap1 GAP activity more than HRas GAP activity; phosphorylation by CDK5 has the opposite effect. Conclusion: Phosphorylation by CaMKII and CDK5 alters the ratio of Rap1 and HRas GAP activities. Significance: Phosphorylation of synGAP by CaMKII and CDK5 can alter the balance of synaptic functions regulated by Ras and Rap.

The skin morphology of cephalopods endows them with remarkable camouflage capabilities. Herein, we report infrared invisibility stickers inspired by the structures and proteins found in cephalopod skin. These stickers enable arbitrary objects to acquire reconfigurable infrared camouflage patterning. Our work represents an initial step towards wearable biomimetic infrared stealth technologies.

SynGAP is a Ras/Rap GTPase-activating protein (GAP) that is a major constituent of postsynaptic densities (PSDs) from mammalian forebrain. Its α1 isoform binds to all three PDZ (PSD-95, Discs-large, ZO-1) domains of PSD-95, the principal PSD scaffold, and can occupy as many as 15% of these PDZ domains. We present evidence that synGAP-α1 regulates the composition of the PSD by restricting binding to the PDZ domains of PSD-95. We show that phosphorylation by Ca2+/calmodulin-dependent protein kinase II (CaMKII) and Polo-like kinase-2 (PLK2) decreases its affinity for the PDZ domains by several fold, which would free PDZ domains for occupancy by other proteins. Finally, we show that three critical postsynaptic signaling proteins that bind to the PDZ domains of PSD-95 are present in higher concentration in PSDs isolated from mice with a heterozygous deletion of synGAP.DOI: http://dx.doi.org/10.7554/eLife.16813.001

Adaptive changes in lysosomal capacity are driven by the transcription factors TFEB and TFE3 in response to increased autophagic flux and endolysosomal stress, yet the molecular details of their activation are unclear. LC3 and GABARAP members of the ATG8 protein family are required for selective autophagy and sensing perturbation within the endolysosomal system. Here, we show that during the conjugation of ATG8 to single membranes (CASM), Parkin-dependent mitophagy, and Salmonella-induced xenophagy, the membrane conjugation of GABARAP, but not LC3, is required for activation of TFEB/TFE3 to control lysosomal capacity. GABARAP directly binds to a previously unidentified LC3-interacting motif (LIR) in the FLCN/FNIP tumor suppressor complex and mediates sequestration to GABARAP-conjugated membrane compartments. This disrupts FLCN/FNIP GAP function toward RagC/D, resulting in impaired substrate-specific mTOR-dependent phosphorylation of TFEB. Thus, the GABARAP-FLCN/ FNIP-TFEB axis serves as a molecular sensor that coordinates lysosomal homeostasis with perturbations and cargo flux within the autophagy-lysosomal network.

Cephalopods have recently emerged as a source of inspiration for the development of novel functional materials. Within this context, a number of studies have explored structural proteins known as reflectins, which play a key role in cephalopod adaptive coloration in vivo and exhibit interesting properties in vitro. Herein, we report an improved high-yield strategy for the preparation and isolation of reflectins in quantities sufficient for materials applications. We first select the Doryteuthis (Loligo) pealeii reflectin A2 (RfA2) isoform as a "model" system and validate our approach for the expression and purification of this protein. We in turn fabricate RfA2-based twoterminal devices and employ both direct and alternating current measurements to demonstrate that RfA2 films conduct protons. Our findings underscore the potential of reflectins as functional materials and may allow a wider range of researchers to investigate their properties.Cephalopods (squid, octopuses, and cuttlesh) are well known for their sophisticated neurophysiology, complex behavior, and stunning camouage displays.1-6 Recently, these animals have drawn signicant attention as sources of novel materials for optical systems, 7-10 biomedical technologies, 11-15 and bioelectronic devices. [16][17][18][19][20] Within this context, a number of literature reports have investigated the properties of unique structural proteins known as reectins, [7][8][9][10]14,[16][17][18][21][22][23][24] which are found in cephalopod skin cells (i.e. leucophores, iridophores, and chromatophores). [25][26][27][28][29][30] In vivo, reectins in general have been shown to play important roles in cephalopod adaptive coloration by serving as components of optically-active ultrastructures, including layered stacks of membrane-enclosed platelets in iridophores, 25,26 membrane-bound arrangements of spherical microparticles in leucophores, 27,28 and interconnected networks of pigment granules in chromatophores. 29,30 In vitro, the Doryteuthis (Loligo) pealeii reectin A1 (RfA1) isoform has found applications in recongurable infrared camouage coatings that are actuated by chemical and mechanical stimuli, 7,8 proton-conducting lms with electrical gures of merit rivaling those of some articial analogues, 16-18 and biocompatible substrates that support the proliferation and differentiation of neural stem cells.14 Overall, reectins' fascinating properties have provided a strong impetus for their continued exploration from both fundamental and applied perspectives.Herein, we describe an improved methodology for the production of difficult-to-handle reectins in quantities sufficient for materials applications. We rst select the Doryteuthis (Loligo) pealeii reectin A2 (RfA2) isoform as a "model" system for electrical characterization and validate a new high-yield strategy for the expression and purication of this precipitation-prone protein. We subsequently fabricate and characterize two-terminal devices for which RfA2 thin lms constitute the active layer. We in tu...

PDZ (PSD-95, DiscsLarge, ZO1) domains function in nature as protein binding domains within scaffold and membrane-associated proteins. They comprise ~ 90 residues and make specific, high affinity interactions with complementary C-terminal peptide sequences, with other PDZ domains, and with phospholipids. We hypothesized that the specific, strong interactions of PDZ domains with their ligands would make them well suited for use in affinity chromatography. Here we describe a novel affinity chromatography method applicable for the purification of proteins that contain PDZ domain-binding ligands, either naturally or introduced by genetic engineering. We created a series of affinity resins comprised of PDZ domains from the scaffold protein PSD-95, or from neuronal nitric oxide synthase (nNOS), coupled to solid supports. We used them to purify heterologously expressed neuronal proteins or protein domains containing endogenous PDZ domain ligands, eluting the proteins with free PDZ domain peptide ligands. We show that Proteins of Interest (POIs) lacking endogenous PDZ domain ligands can be engineered as fusion products containing C-terminal PDZ domain ligand peptides or internal, N- or C-terminal PDZ domains and then can be purified by the same method. Using this method, we recovered recombinant GFP fused to a PDZ-domain ligand in active form as verified by fluorescence yield. Similarly, chloramphenicol acetyltransferase (CAT) and β-Galactosidase (LacZ) fused to a C-terminal PDZ domain ligand or an N-terminal PDZ domain were purified in active form as assessed by enzymatic assay. In general, PDZ domains and ligands derived from PSD-95 were superior to those from nNOS for this method. PDZ Domain Affinity Chromatography promises to be a versatile and effective method for purification of a wide variety of natural and recombinant proteins.