The STIM1 CTID domain determines access of SARAF to SOAR to regulate Orai1 channel function

Ca²⁺ influx by store-operated Ca²⁺ channels (SOCs) mediates all Ca²⁺-dependent cell functions, but excess Ca²⁺ influx is highly toxic. The molecular components of SOC are the pore-forming Orai1 channel and the endoplasmic reticulum Ca²⁺ sensor STIM1. Slow Ca²⁺-dependent inactivation (SCDI) of Orai1 guards against cell damage, but its molecular mechanism is unknown. Here, we used homology modeling to identify a conserved STIM1(448–530) C-terminal inhibitory domain (CTID), whose deletion resulted in spontaneous clustering of STIM1 and full activation of Orai1 in the absence of store depletion. CTID regulated SCDI by determining access to and interaction of the STIM1 inhibitor SARAF with STIM1 Orai1 activation region (SOAR), the STIM1 domain that activates Orai1. CTID had two lobes, STIM1(448–490) and STIM1(490–530), with distinct roles in mediating access of SARAF to SOAR. The STIM1(448–490) lobe restricted, whereas the STIM1(490–530) lobe directed, SARAF to SOAR. The two lobes cooperated to determine the features of SCDI. These findings highlight the central role of STIM1 in SCDI and provide a molecular mechanism for SCDI of Orai1.     

Characterization of a novel xylanase from Armillaria gemina and its immobilization onto SiO2 nanoparticles

Enhanced catalytic activities of different lignocellulases were obtained from Armillaria gemina under statistically optimized parameters using a jar fermenter. This strain showed maximum xylanase, endoglucanase, cellobiohydrolase, and β-glucosidase activities of 1,270, 146, 34, and 15 U mL^?1, respectively. Purified A. gemina xylanase (AgXyl) has the highest catalytic efficiency (k _cat/K _m?=?1,440 mg?mL^?1?s^?1) ever reported for any fungal xylanase, highlighting the significance of the current study. We covalently immobilized the crude xylanase preparation onto functionalized silicon oxide nanoparticles, achieving 117 % immobilization efficiency. Further immobilization caused a shift in the optimal pH and temperature, along with a fourfold improvement in the half-life of crude AgXyl. Immobilized AgXyl gave 37.8 % higher production of xylooligosaccharides compared to free enzyme. After 17 cycles, the immobilized enzyme retained 92 % of the original activity, demonstrating its potential for the synthesis of xylooligosaccharides in industrial applications.     

Urban land use limits regional bumble bee gene flow

Potential declines in native pollinator communities and increased reliance on pollinator‐dependent crops have raised concerns about native pollinator conservation and dispersal across human‐altered landscapes. Bumble bees are one of the most effective native pollinators and are often the first to be extirpated in human‐altered habitats, yet little is known about how bumble bees move across fine spatial scales and what landscapes promote or limit their gene flow. In this study, we examine regional genetic differentiation and fine‐scale relatedness patterns of the yellow‐faced bumble bee, Bombus vosnesenskii, to investigate how current and historic habitat composition impact gene flow. We conducted our study across a landscape mosaic of natural, agricultural and urban/suburban habitats, and we show that B. vosnesenskii exhibits low but significant levels of differentiation across the study system (F_ST = 0.019, D_est = 0.049). Most importantly, we reveal significant relationships between pairwise F_ST and resistance models created from contemporary land use maps. Specifically, B. vosnesenskii gene flow is most limited by commercial, industrial and transportation‐related impervious cover. Finally, our fine‐scale analysis reveals significant but declining relatedness between individuals at the 1–9 km spatial scale, most likely due to local queen dispersal. Overall, our results indicate that B. vosnesenskii exhibits considerable local dispersal and that regional gene flow is significantly limited by impervious cover associated with urbanization.     

Antioxidant efficacy and adhesion rescue by a recombinant mussel foot protein‐6

Mytilus foot protein type 6 (mfp‐6) is crucial for maintaining the reducing conditions needed for optimal wet adhesion in marine mussels. In this report, we describe the expression and production of a recombinant Mytilus californianus foot protein type 6 variant 1 (rmfp‐6.1) fused with a hexahistidine affinity tag in Escherichia coli and its purification by affinity chromatography. Recombinant mfp‐6 showed high purification yields of 5–6 mg L^?1 cell culture and excellent solubility in low pH buffers that retard oxidation of its many thiol groups. Purified rmfp‐6.1 protein showed high 2,2‐diphenyl‐1‐picrylhydrazyl radical scavenging activity when compared with vitamin C. Using the highly sensitive surface forces apparatus (SFA) technique to measure interfacial surface forces in the nano‐Newton range, we show that rmfp‐6.1 is also able to rescue the oxidation‐dependent adhesion loss of mussel foot protein 3 (mfp‐3) at pH 3. The adhesion rescue is related to a reduction of dopaquinone back to 3,4‐dihydroxyphenyl‐l ‐alanine in mfp‐3, which is the reverse reaction observed during the detrimental enzymatic browning process in fruits and vegetables. Broadly viewed, rmfp‐6.1 has potential as a versatile antioxidant for applications ranging from personal products to antispoilants for perishable foods during processing and storage. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:1587–1593, 2013