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Substrate-binding proteins (SBPs) play an important role in solute uptake and signal transduction. In 2010, Berntsson et al. classified the 114 organism-specific SBP structures available at that time and defined six protein clusters, based on their structural similarity. Since then, the number of unique SBP structures has increased almost fivefold, whereas the number of protein entries in the Protein Data Bank (PDB) nearly doubled. On the basis of the much larger dataset, we now subclassify the SBPs within the original clusters. Moreover, we propose a 7th cluster based on a small group of SBPs with structural features significantly different from those observed in the other proteins., (© 2016 Federation of European Biochemical Societies.)

SecYEG functions as a membrane channel for protein export. SecY constitutes the protein-conducting pore, which is enwrapped by SecE in a V-shaped manner. In its minimal form SecE consists of a single transmembrane segment that is connected to a surface-exposed amphipathic α-helix via a flexible hinge. These two domains are the major sites of interaction between SecE and SecY. Specific cleavage of SecE at the hinge region, which destroys the interaction between the two SecE domains, reduced translocation. When SecE and SecY were disulfide bonded at the two sites of interaction, protein translocation was not affected. This suggests that the SecY and SecE interactions are static, while the hinge region provides flexibility to allow the SecY pore to open., (Copyright © 2013 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.)