CRM1 (also known as XPO1 and exportin 1) mediates nuclear export of hundreds of proteins through the recognition of the leucine-rich nuclear export signal (LR-NES). Here we present the 2.9Å structure of CRM1 bound to snurportin 1 (SNUPN). Snurportin 1 binds CRM1 in a bipartite manner by means of an amino-terminal LR-NES and its nucleotide-binding domain. The LR-NES is a combined α-helical-extended structure that occupies a hydrophobic groove between two CRM1 outer helices. The LR-NES interface explains the consensus hydrophobic pattern, preference for intervening electronegative residues and inhibition by leptomycin B. The second nuclear export signal epitope is a basic surface on the snurportin 1 nucleotide-binding domain, which binds an acidic patch on CRM1 adjacent to the LR-NES site. Multipartite recognition of individually weak nuclear export signal epitopes may be common to CRM1 substrates, enhancing CRM1 binding beyond the generally low affinity LR-NES. Similar energetic construction is also used in multipartite nuclear localization signals to provide broad substrate specificity and rapid evolution in nuclear transport.

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CRM1 (or exportin 1, Xpo1) transports proteins out of the cell nucleus through the nuclear pore complex. In the cytoplasm, GTP hydrolysis and consequent dissociation of Ran from CRM1 releases low-affinity substrates, while additional factors facilitate release of high-affinity substrates. Here we provide a model for human CRM1 export complex assembly and disassembly through structural and biochemical analyses of CRM1 bound to the substrate snurportin 1 (SNUPN, also called snuportin 1).

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Nectins are Ca2؉ -independent immunoglobulin (Ig) superfamily proteins that participate in the organization of epithelial and endothelial junctions. Nectins have three Ig-like domains in the extracellular region, and the first one is essential in cell-cell adhesion and plays a central role in the interaction with the envelope glycoprotein D of several viruses. Five Nectin-like molecules (Necl-1 through -5) with similar domain structures to those of Nectins have been identified. Necl-1 is specifically expressed in neural tissue, has Ca 2؉ -independent homophilic and heterophilic cell-cell adhesion activity, and plays an important role in the formation of synapses, axon bundles, and myelinated axons. Here we report the first crystal structure of its N-terminal Ig-like V domain at 2.4 Å , providing insight into trans-cellular recognition mediated by Necl-1. The protein crystallized as a dimer, and the dimeric form was confirmed by size-exclusion chromatography and chemical cross-linking experiments, indicating this V domain is sufficient for homophilic interaction. Mutagenesis work demonstrated that Phe 82 is a key residue for the adhesion activity of Necl-1. A model for homophilic adhesion of Necl-1 at synapses is proposed based on its structure and previous studies.The cell-cell adhesion systems play important roles in neuronal cell migration, axon-bundle formation, target-cell recognition, activity-dependent plasticity of synapses, and formation of complex glial networks, which surround axons and synapses (1). Nectins are a novel family of Ca 2ϩ -independent immunoglobulin-like cell-cell adhesion molecules and comprise four members, termed Nectin-1 to Nectin-4 (2, 3). All Nectins have an extracellular region of three Ig-like domains, a single transmembrane region, and a cytoplasmic tail region (see Fig. 1) (2, 3). Each Nectin forms a homo-cis-dimer, in which the monomers are aligned in a parallel orientation, which is then followed by formation of homo-trans-dimers in which cis-dimers from opposing cell surfaces interact in an anti-parallel orientation, causing cell-cell adhesion (4 -8).The first Ig-like domain is necessary and sufficient for the formation of homo-trans-dimers, whereas the second Ig-like domain is necessary for the formation of homo-cis-dimers (5, 7-9). Furthermore, Nectin-3 can also form a hetero-trans-dimer with either Nectin-1 or -2, whereas Nectin-4 also forms a hetero-trans-dimer with Nectin-1 (4). The heterotrans-dimers are also mediated by the V domains (9). Nectin-1 has been confirmed to serve as a receptor for all ␣-herpes viruses tested so far, including herpes simplex virus (HSV) 3 type 1, HSV type 2, and pseudorabies virus, facilitating their entry and cell-cell spread (10, 11). Furthermore, the V domain of Nectin-1 has been demonstrated to play a central role in the interaction with the envelope glycoprotein D of HSV, pseudorabies virus, and bovine herpes virus-1 (12, 13). Therefore, the V domain plays an essential role not only in homophilic and heterophilic trans-interactions but ...

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The effect of high‐pressure homogenization (HPH) at 0.1 (control), 40 or 80 MPa on the denatured peanut protein were investigated. Solubility, emulsifying property, foaming property, differential scanning calorimetry (DSC) characteristic, water‐holding capacity (WHC) and scanning electron microscope (SEM) analysis of the peanut protein isolates (PPIs) from the peanut flour after various HPH treatments were analyzed. Increased solubility of the denatured peanut protein by HPH treatment depended on the pH value. In the range of pH 4−7, the HPH‐treated peanut protein exhibited a higher solubility than the non‐HPH‐treated protein, but the HPH treatment did not affect significantly the solubility in the range of pH 8−10. HPH treatment improved the emulsifying activity index (EAI) and foaming capacity (FC) but reduced the emulsifying stability index and foaming stability. In addition, HPH treatment markedly improved the WHC but slightly affected the DSC parameter. Based on the observation of SEM, many irregular fine crackles in the peanut protein after HPH treatment appeared, which showed that the treatment resulted in the change in the surface microstructure of the protein. These results indicated that the HPH treatment led to the modification of the microstructure of peanut protein and, thus, improved its functional properties such as EAI, FC and WHC. PRACTICAL APPLICATIONS Functional properties of plant and animal proteins are important in food processing and production formulation. Peanut exhibits an excellent potential as a source of plant proteins. Improvement of functional or nutritional properties of proteins can help produce some novel food products in food industry. The use of high‐pressure homogenization (HPH) is one of the most efficient means to improve the functional properties of plant proteins. The study exhibited that application of HPH treatment resulted in the changed the microstructure of peanut protein and, thus, improved its functional properties such as the emulsifying activity index, foam capacity and water‐holding capacity, which might be utilized in food industry.