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Many proteins must translocate through the protein-conducting Sec61 channel in the eukaryotic endoplasmic reticulum membrane or the SecY channel in the prokaryotic plasma membrane.sup.1,2. Proteins with highly hydrophobic signal sequences are first recognized by the signal recognition particle (SRP).sup.3,4 and then moved co-translationally through the Sec61 or SecY channel by the associated translating ribosome. Substrates with less hydrophobic signal sequences bypass the SRP and are moved through the channel post-translationally.sup.5,6. In eukaryotic cells, post-translational translocation is mediated by the association of the Sec61 channel with another membrane protein complex, the Sec62-Sec63 complex.sup.7-9, and substrates are moved through the channel by the luminal BiP ATPase.sup.9. How the Sec62-Sec63 complex activates the Sec61 channel for post-translational translocation is not known. Here we report the electron cryo-microscopy structure of the Sec complex from Saccharomyces cerevisiae, consisting of the Sec61 channel and the Sec62, Sec63, Sec71 and Sec72 proteins. Sec63 causes wide opening of the lateral gate of the Sec61 channel, priming it for the passage of low-hydrophobicity signal sequences into the lipid phase, without displacing the channel's plug domain. Lateral channel opening is triggered by Sec63 interacting both with cytosolic loops in the C-terminal half of Sec61 and transmembrane segments in the N-terminal half of the Sec61 channel. The cytosolic Brl domain of Sec63 blocks ribosome binding to the channel and recruits Sec71 and Sec72, positioning them for the capture of polypeptides associated with cytosolic Hsp70.sup.10. Our structure shows how the Sec61 channel is activated for post-translational protein translocation.The cryo-EM structure of the post-translational protein translocation machinery of the endoplasmic reticulum membrane shows that Sec63 opens the channel, enabling insertion of low-hydrophobicity signal sequences into the lipid phase., Author(s): Xudong Wu [sup.1] [sup.2] , Cerrone Cabanos [sup.1] [sup.2] , Tom A. Rapoport [sup.1] [sup.2] Author Affiliations:(1) Howard Hughes Medical Institute, Harvard Medical School, Boston, USA(2) Department of Cell [...]

Coconut stores its lipid reserves in the endosperm, specifically in oil bodies that contain proteins called oleosins which stabilise their structure. This study reports the complete cDNA sequences of 3 genes for 3 isoforms of oleosin termed CnOLE500a, CnOLE500c, and CnOLE300a with 396, 375, and 381 nucleotides, respectively. Their predicted amino acid sequences were 131, 124, and 126 residues in length, respectively, with molecular weights of 13,787, 12,982, and 12,988 Da, respectively. The complete CnOLE500a cDNA sequence had 83.1% similarity with that of CnOLE500c, while CnOLE300a cDNA had only 50.7% and 46.5% similarity with CnOLE500a and CnOLE500c, respectively. None of the 3 coconut oleosins had the 18 amino acid insertion characteristics of H-class oleosins, thus they belonged to the L-class of oleosins. However, phylogenetic analysis showed that CnOLE300a was more related to H-class oleosins from dicots. All 3 isoforms were highly expressed at all stages of coconut endosperm development. CnOLE500c exhibited 6% higher expression than CnOLE500a and 15% higher than CnOLE300a at all stages of coconut endosperm development. However, oleosin proteins were barely detectable in the solid endosperm of coconut at 5-6 months, but this increased 20-fold at 6-7 months, and increased by a further 2- and 12-fold, at 7-8 and 8-9 months, respectively. [ABSTRACT FROM AUTHOR]

• Soybean is one of the most important sources of plant protein for agricultural, food and industrial applications as well as health benefits. • Bioactive peptides have a beneficial effect on health by demonstrating various possible physiological roles in the body. • Significant advances in using soybean seed as bioreactor as well as to enhance its protein quality have been successfully carried out. • Elucidating the molecular mechanism of soybean storage protein trafficking will aid in the design of novel soybean crops with enhanced activity. • The design of novel soybean crops with enhanced protein functional activity can also serve as model for protein engineering other crops. Soybean is one of the most important sources of plant protein and is known for its wide range of agricultural, food, and industrial applications as well as health benefits. Interest in soybean proteins has been steadily growing as progressively more applications and benefits are discovered. This review article is focused on the major seed storage proteins of soybean, their three-dimensional structures, their nutritional importance and bioactive peptides, cellular synthesis, and accumulation in seeds. This will also summarize past efforts in the recombinant production of foreign proteins or bioactive peptides in soybean seed. [ABSTRACT FROM AUTHOR]

Lipid regulation of ion channels by low-abundance signaling lipids phosphatidylinositol 4,5-bisphosphate (PIP 2 ) and phosphatidic acid (PA) has emerged as a central cellular mechanism for controlling ion channels and the excitability of nerves. A lack of robust assays suitable for facile detection of a lipid bound to a channel has hampered the probing of the lipid binding sites and measuring the pharmacology of putative lipid agonists for ion channels. Here, we show a fluorescent PIP 2 competition assay for detergent-purified potassium channels, including TWIK-1-related K + -channel (TREK-1). Anionic lipids PA and phosphatidylglycerol (PG) bind dose dependently (9.1 and 96 μM, respectively) and agonize the channel. Our assay shows PIP 2 binds with high affinity (0.87 μM) but surprisingly can directly antagonize TREK-1 in liposomes. We propose a model for TREK-1 lipid regulation where PIP 2 can compete with PA and PG agonism based on the affinity of the lipid for a site within the channel., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)

Improving the nutraceutical value of rice would positively impact the health and well-being of rice consumers worldwide. Based on the three-dimensional structure of soybean beta-conglycinin, we designed a beta subunit with a strong phagocytosis-stimulating activity (mbeta subunit). Here, we describe the genetic modification and production of rice seeds containing the mbeta subunit as part of our aim to develop a food material that promotes human health. The mbeta subunit folded correctly and was accumulated in the protein body II of rice seeds at a level similar to wild-type beta subunit. Mutant beta subunit purified from transgenic rice seeds exhibited high phagocytosis-stimulating activity, demonstrating its potential value in enhancing the nutritional value of rice., (Copyright 2010 Elsevier Inc. All rights reserved.)