Search results for "allosteric regulation"
showing 10 items of 90 documents
Regulatory properties of 6-phosphofructokinase and control of glycolysis in boar spermatozoa.
2007
Glycolysis is crucial for sperm functions (motility and fertilization), but how this pathway is regulated in spermatozoa is not clear. This prompted to study the location and the regulatory properties of 6-phosphofructokinase (PFK, EC 2.7.1.11), the most important element for control of glycolytic flux. Unlike some other glycolytic enzymes, PFK showed no tight binding to sperm structures. It could readily be extracted from ejaculated boar spermatozoa by sonication and was then chromatographically purified. At physiological pH, the enzyme was allosterically inhibited by near-physiological concentrations of its co-substrate ATP, which induced co-operativity, i.e. reduced the affinity for the …
Identification and quantification of a new family of peptide endocannabinoids (Pepcans) showing negative allosteric modulation at CB1 receptors.
2012
The α-hemoglobin-derived dodecapeptide RVD-hemopressin (RVDPVNFKLLSH) has been proposed to be an endogenous agonist for the cannabinoid receptor type 1 (CB(1)). To study this peptide, we have raised mAbs against its C-terminal part. Using an immunoaffinity mass spectrometry approach, a whole family of N-terminally extended peptides in addition to RVD-Hpα were identified in rodent brain extracts and human and mouse plasma. We designated these peptides Pepcan-12 (RVDPVNFKLLSH) to Pepcan-23 (SALSDLHAHKLRVDPVNFKLLSH), referring to peptide length. The most abundant Pepcans found in the brain were tested for CB(1) receptor binding. In the classical radioligand displacement assay, Pepcan-12 was th…
Bis-cyclohexyl-crown-ethers as allosteric carriers
1992
Abstract Several bis-cyclohexyl-crown-ethers have been synthesized and used as carriers for alkaline cations. These compounds should all show negative allosteric cooperativity, but only 1 exhibits an odd cation transport behavior across the liquid organic membranes.
A lipid transfer protein binds to a receptor involved in the control of plant defence responses
2001
AbstractLipid transfer proteins (LTPs) and elicitins are both able to load and transfer lipidic molecules and share some structural and functional properties. While elicitins are known as elicitors of plant defence mechanisms, the biological function of LTP is still an enigma. We show that a wheat LTP1 binds with high affinity sites. Binding and in vivo competition experiments point out that these binding sites are common to LTP1 and elicitins and confirm that they are the biological receptors of elicitins. A mathematical analysis suggests that these receptors could be represented by an allosteric model corresponding to an oligomeric structure with four identical subunits.
Selective recognition of neutral guests in an aqueous medium by a biomimetic calix[6]cryptamide receptor
2015
The design of artificial receptors that can efficiently work in water is a challenging research area. A possible biomimetic approach for the elaboration of such receptors consists of associating a hydrophobic cavity with a polar polyfunctional binding site. On this basis, a hydrophilic calix[6]cryptamide decorated with oligo(ethylene glycol) units (i.e. 8) was synthesized through an efficient [1 + 1] macrocyclization reaction as the key-step. The complexation of neutral molecules was evaluated by NMR spectroscopy through competition experiments either in apolar or aqueous media. In both media, host 8 can bind neutral species that display H-bonding acceptor and donor groups such as amides or…
All hierarchical levels are involved in conformational transitions of the 4×6-meric tarantula hemocyanin upon oxygenation
2002
The respiratory protein of the tarantula Eurypelma californicum is a 4 x 6-meric hemocyanin that binds oxygen with high cooperativity. This requires the existence of different conformations which have been confirmed by small angle X-ray scattering (SAXS). Here we present reconstructed 3D-models of the oxy- and deoxy-forms of tarantula hemocyanins, as obtained by fitting small angle X-rays scattering curves on the basis of known X-ray structures and electron microscopy of related hemocyanins. For the first time, the involvement of movements at all levels of the quaternary structure was confirmed for an arthropod hemocyanin upon oxygenation. The two identical 2 x 6-meric half-molecules of the…
Nautilus pompilius Hemocyanin: 9 Å Cryo-EM Structure and Molecular Model Reveal the Subunit Pathway and the Interfaces between the 70 Functional Units
2007
Hemocyanins are giant extracellular oxygen carriers in the hemolymph of many molluscs. Nautilus pompilius (Cephalopoda) hemocyanin is a cylindrical decamer of a 350 kDa polypeptide subunit that in turn is a "pearl-chain" of seven different functional units (FU-a to FU-g). Each globular FU has a binuclear copper centre that reversibly binds one O(2) molecule, and the 70-FU decamer is a highly allosteric protein. Its primary structure and an 11 A cryo-electron microscopy (cryo-EM) structure have recently been determined, and the crystal structures of two related FU types are available in the databanks. However, in molluscan hemocyanin, the precise subunit pathway within the decamer, the inter…
The Monod-Wyman-Changeux allosteric model accounts for the quaternary transition dynamics in wild type and a recombinant mutant human hemoglobin
2012
International audience; The acknowledged success of the Monod-Wyman-Changeux (MWC) allosteric model stems from its efficacy in accounting for the functional behavior of many complex proteins starting with hemoglobin (the paradigmatic case) and extending to channels and receptors. The kinetic aspects of the allosteric model, however, have been often neglected, with the exception of hemoglobin and a few other proteins where conformational relaxations can be triggered by a short and intense laser pulse, and monitored by time-resolved optical spectroscopy. Only recently the application of time-resolved wide-angle X-ray scattering (TR-WAXS), a direct structurally sensitive technique, unveiled th…
Small-angle X-ray Scattering-based Three-dimensional Reconstruction of the Immunogen KLH1 Reveals Different Oxygen-dependent Conformations
2003
For decades the respiratory protein keyhole limpet hemocyanin (KLH1) from the marine gastropod Megathura crenulata has been used widely as a potent immunostimulant, useful hapten carrier, and valuable agent in the treatment of bladder carcinoma. Although much information on the immunological properties of KLH1 is available, biochemical and structural data are still incomplete. Small-angle x-ray scattering revealed the existence of two conformations, an oxy state being slightly more compact than the deoxy state. Based on small-angle scattering curves, a newly developed Monte Carlo algorithm delivered a surface representation of proteins. The massive changes of the surfaces of reconstructed d…
Structural and Functional Basis for Understanding the Biological Significance of P2X7 Receptor
2020
The P2X7 receptor (P2X7R) possesses a unique structure associated to an as yet not fully understood mechanism of action that facilitates cell permeability to large ionic molecules through the receptor itself and/or nearby membrane proteins. High extracellular adenosine triphosphate (ATP) levels—inexistent in physiological conditions—are required for the receptor to be triggered and contribute to its role in cell damage signaling. The inconsistent data on its activation pathways and the few studies performed in natively expressed human P2X7R have led us to review the structure, activation pathways, and specific cellular location of P2X7R in order to analyze its biological relevance. The ATP-…