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Membrane channel proteins of the aquaporin family are highly selective for permeation of specific small molecules, with absolute exclusion of ions and charged solutes and without dissipation of the electrochemical potential across the cell membrane. We report the crystal structure of the Escherichia coli glycerol facilitator (GlpF) with its primary permeant(More)
The signal recognition particle (SRP) and its membrane-associated receptor (SR) catalyze targeting of nascent secretory and membrane proteins to the protein translocation apparatus of the cell. Components of the SRP pathway and salient features of the molecular mechanism of SRP-dependent protein targeting are conserved in all three kingdoms of life. Recent(More)
The first structure of an ammonia channel from the Amt/MEP/Rh protein superfamily, determined to 1.35 angstrom resolution, shows it to be a channel that spans the membrane 11 times. Two structurally similar halves span the membrane with opposite polarity. Structures with and without ammonia or methyl ammonia show a vestibule that recruits NH4+/NH3, a(More)
Quinoxalinedione compounds such as 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) are the most commonly used alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonists. However, we find that in the presence of transmembrane AMPA receptor regulatory proteins (TARPs), which are AMPA receptor auxiliary subunits, CNQX acts as a partial(More)
Aberrant folding of proteins in the endoplasmic reticulum activates the bifunctional transmembrane kinase/endoribonuclease Ire1. Ire1 excises an intron from HAC1 messenger RNA in yeasts and Xbp1 messenger RNA in metozoans encoding homologous transcription factors. This non-conventional mRNA splicing event initiates the unfolded protein response, a(More)
The crystal structure of the signal sequence binding subunit of the signal recognition particle (SRP) from Thermus aquaticus reveals a deep groove bounded by a flexible loop and lined with side chains of conserved hydrophobic residues. The groove defines a flexible, hydrophobic environment that is likely to contribute to the structural plasticity necessary(More)
Unfolded proteins in the endoplasmic reticulum (ER) activate the ER transmembrane sensor Ire1 to trigger the unfolded protein response (UPR), a homeostatic signaling pathway that adjusts ER protein folding capacity according to need. Ire1 is a bifunctional enzyme, containing cytoplasmic kinase and RNase domains whose roles in signal transduction downstream(More)
Human erythropoietin is a haematopoietic cytokine required for the differentiation and proliferation of precursor cells into red blood cells. It activates cells by binding and orientating two cell-surface erythropoietin receptors (EPORs) which trigger an intracellular phosphorylation cascade. The half-maximal response in a cellular proliferation assay is(More)
Rigid body rotation of five domains and movements within their interfacial joints provide a rational context for understanding why HIV protease mutations that arise in drug resistant strains are often spatially removed from the drug or substrate binding sites. Domain motions associated with substrate binding in the retroviral HIV-1 and SIV proteases are(More)