Search results for "Protein subunit"
showing 10 items of 243 documents
Quaternary structure of the European spiny lobster (Palinurus elephas) 1x6-mer hemocyanin from cryoEM and amino acid sequence data.
2002
Abstract Arthropod hemocyanins are large respiratory proteins that are composed of up to 48 subunits (8×6-mer) in the 75 kDa range. A 3D reconstruction of the 1×6-mer hemocyanin from the European spiny lobster Palinurus elephas has been performed from 9970 single particles using cryoelectron microscopy. An 8 A resolution of the hemocyanin 3D reconstruction has been obtained from about 600 final class averages. Visualisation of structural elements such as α-helices has been achieved. An amino acid sequence alignment shows the high sequence identity (>80%) of the hemocyanin subunits from the European spiny lobster P. elephas and the American spiny lobster Panulirus interruptus . Comparison of…
Synthesis of GABAA receptor agonists and evaluation of their alpha-subunit selectivity and orientation in the GABA binding site.
2008
Drugs used to treat various disorders target GABA A receptors. To develop alpha subunit selective compounds, we synthesized 5-(4-piperidyl)-3-isoxazolol (4-PIOL) derivatives. The 3-isoxazolol moiety was substituted by 1,3,5-oxadiazol-2-one, 1,3,5-oxadiazol-2-thione, and substituted 1,2,4-triazol-3-ol heterocycles with modifications to the basic piperidine substituent as well as substituents without basic nitrogen. Compounds were screened by [(3)H]muscimol binding and in patch-clamp experiments with heterologously expressed GABA A alpha ibeta 3gamma 2 receptors (i = 1-6). The effects of 5-aminomethyl-3 H-[1,3,4]oxadiazol-2-one 5d were comparable to GABA for all alpha subunit isoforms. 5-pipe…
Ligand-binding domain determines endoplasmic reticulum exit of AMPA receptors.
2010
AMPA receptors (AMPARs) are tetrameric ion channels that mediate rapid glutamate signaling in neurons and many non-neuronal cell types. Endoplasmic reticulum (ER) quality control mechanisms permit only correctly folded functional receptors to be delivered to the cell surface. We analyzed the biosynthetic maturation and transport of all 12 GluA1–4 subunit splice variants as homomeric receptors and observed robust isoform-dependent differences in ER exit competence and surface expression. In contrast to inefficient ER exit of both GluA3 splice forms and the flop variants of GluA1 and GluA4, prominent plasma membrane expression was observed for the other AMPAR isoforms. Surprisingly, deletion …
Complete subunit sequences, structure and evolution of the 6 x 6-mer hemocyanin from the common house centipede, Scutigera coleoptrata.
2003
Hemocyanins are large oligomeric copper-containing proteins that serve for the transport of oxygen in many arthropod species. While studied in detail in the Chelicerata and Crustacea, hemocyanins had long been considered unnecessary in the Myriapoda. Here we report the complete molecular structure of the hemocyanin from the common house centipede Scutigera coleoptrata (Myriapoda: Chilopoda), as deduced from 2D-gel electrophoresis, MALDI-TOF mass spectrometry, protein and cDNA sequencing, and homology modeling. This is the first myriapod hemocyanin to be fully sequenced, and allows the investigation of hemocyanin structure-function relationship and evolution. S. coleoptrata hemocyanin is a 6…
Structure of Mega-Hemocyanin Reveals Protein Origami in Snails
2014
SummaryMega-hemocyanin is a 13.5 MDa oxygen transporter found in the hemolymph of some snails. Similar to typical gastropod hemocyanins, it is composed of 400 kDa building blocks but has additional 550 kDa subunits. Together, they form a large, completely filled cylinder. The structural basis for this highly complex protein packing is not known so far. Here, we report the electron cryomicroscopy (cryo-EM) structure of mega-hemocyanin complexes from two different snail species. The structures reveal that mega-hemocyanin is composed of flexible building blocks that differ in their conformation, but not in their primary structure. Like a protein origami, these flexible blocks are optimally pac…
A human CCT5 gene mutation causing distal neuropathy impairs hexadecamer assembly in an archaeal model
2014
Chaperonins mediate protein folding in a cavity formed by multisubunit rings. The human CCT has eight non-identical subunits and the His147Arg mutation in one subunit, CCT5, causes neuropathy. Knowledge is scarce on the impact of this and other mutations upon the chaperone's structure and functions. To make progress, experimental models must be developed. We used an archaeal mutant homolog and demonstrated that the His147Arg mutant has impaired oligomeric assembly, ATPase activity, and defective protein homeostasis functions. These results establish for the first time that a human chaperonin gene defect can be reproduced and studied at the molecular level with an archaeal homolog. The major…
Proteome response of Tribolium castaneum larvae to Bacillus thuringiensis toxin producing strains.
2012
Susceptibility of Tribolium castaneum (Tc) larvae was determined against spore-crystal mixtures of five coleopteran specific and one lepidopteran specific Bacillus thuringiensis Cry toxin producing strains and those containing the structurally unrelated Cry3Ba and Cry23Aa/Cry37Aa proteins were found toxic (LC(50) values 13.53 and 6.30 µg spore-crystal mixture/µL flour disc, respectively). Using iTRAQ combined with LC-MS/MS allowed the discovery of seven novel differentially expressed proteins in early response of Tc larvae to the two active spore-crystal mixtures. Proteins showing a statistically significant change in treated larvae compared to non-intoxicated larvae fell into two major cat…
Structural Characterization of Set1 RNA Recognition Motifs and their Role in Histone H3 Lysine 4 Methylation
2006
Departament de Bioquimica iBiologia Molecular, Universitatde Valencia, C/Dr Moliner 50,46100, Burjassot, SpainThe yeast Set1 histone H3 lysine 4 (H3K4) methyltransferase contains, inaddition to its catalytic SET domain, a conserved RNA recognition motif(RRM1). We present here the crystal structure and the secondary structureassignment in solution of the Set1 RRM1. Although RRM1 has the expectedβαββαβ RRM-fold, it lacks the typical RNA-binding features of thesemodules. RRM1 is not able to bind RNA by itself in vitro, but a constructcombining RRM1 with a newly identified downstream RRM2 specificallybinds RNA. Invivo,H3K4 methylation isnot affectedbyapoint mutation inRRM2 that preserves Set1 s…
Crystallization and Preliminary Analysis of Crystals of the 24-Meric Hemocyanin of the Emperor Scorpion (Pandinus imperator)
2011
Hemocyanins are giant oxygen transport proteins found in the hemolymph of several invertebrate phyla. They constitute giant multimeric molecules whose size range up to that of cell organelles such as ribosomes or even small viruses. Oxygen is reversibly bound by hemocyanins at binuclear copper centers. Subunit interactions within the multisubunit hemocyanin complex lead to diverse allosteric effects such as the highest cooperativity for oxygen binding found in nature. Crystal structures of a native hemocyanin oligomer larger than a hexameric substructure have not been published until now. We report for the first time growth and preliminary analysis of crystals of the 24-meric hemocyanin (M(…
Cockroach allergens Per a 3 are oligomers
2009
Allergens from cockroaches cause major asthma-related health problems worldwide. Among them Per a 3 belongs to the most potent allergens. Although the sequences of some members of the Per a 3-family are known, their biochemical and biophysical properties have not been investigated. Here we present for the first time a thorough structural characterization of these allergens, which have recently been tested to induce an increase of allergy specific indicators in blood of Europeans. We isolated two Per a 3 isoforms, which occur freely dissolved in the hemolymph as hexamers with molecular masses of 465+/-25kDa (P II) and 512+/-25kDa (P I). Their sedimentation coefficients (S(20,W)) were determi…