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Membrane Enzyme (membrane + enzyme)
Selected AbstractsFunctional analysis of the large periplasmic loop of the Escherichia coli K-12 WaaL O-antigen ligaseMOLECULAR MICROBIOLOGY, Issue 6 2008José M. Pérez Summary WaaL is a membrane enzyme implicated in ligating undecaprenyl-diphosphate (Und-PP)-linked O antigen to lipid A-core oligosaccharide. We determined the periplasmic location of a large (EL5) and small (EL4) adjacent loops in the Escherichia coli K-12 WaaL. Structural models of the EL5 from the K-12, R1 and R4 E. coli ligases were generated by molecular dynamics. Despite the poor amino acid sequence conservation among these proteins, the models afforded similar folds consisting of two pairs of almost perpendicular ,-helices. One ,-helix in each pair contributes a histidine and an arginine facing each other, which are highly conserved in WaaL homologues. Mutations in either residue rendered WaaL non-functional, since mutant proteins were unable to restore O antigen surface expression. Replacements of residues located away from the putative catalytic centre and non-conserved residues within the centre itself did not affect ligation. Furthermore, replacing a highly conserved arginine in EL4 with various amino acids inactivates WaaL function, but functionality reappears when the positive charge is restored by a replacement with lysine. These results lead us to propose that the conserved amino acids in the two adjacent periplasmic loops could interact with Und-PP, which is the common component in all WaaL substrates. [source] Chemical shift assignment of the transmembrane helices of DsbB, a 20-kDa integral membrane enzyme, by 3D magic-angle spinning NMR spectroscopyPROTEIN SCIENCE, Issue 2 2008Ying Li Abstract The Escherichia coli inner membrane enzyme DsbB catalyzes disulfide bond formation in periplasmic proteins, by transferring electrons to ubiquinone from DsbA, which in turn directly oxidizes cysteines in substrate proteins. We have previously shown that DsbB can be prepared in a state that gives highly resolved magic-angle spinning (MAS) NMR spectra. Here we report sequential 13C and 15N chemical shift assignments for the majority of the residues in the transmembrane helices, achieved by three-dimensional (3D) correlation experiments on a uniformly 13C, 15N-labeled sample at 750-MHz 1H frequency. We also present a four-dimensional (4D) correlation spectrum, which confirms assignments in some highly congested regions of the 3D spectra. Overall, our results show the potential to assign larger membrane proteins using 3D and 4D correlation experiments and form the basis of further structural and dynamical studies of DsbB by MAS NMR. [source] Fatty Acid Amide Hydrolase: From Characterization to TherapeuticsCHEMISTRY & BIODIVERSITY, Issue 8 2007Geoffray Labar Abstract Fatty acid amide hydrolase (FAAH) is an integral membrane enzyme within the amidase-signature family that terminates the action of several endogenous lipid messengers, including oleamide and the endocannabinoid anandamide. The hydrolysis of such messengers leads to molecules devoid of biological activity, and, therefore, modulates a number of neurobehavioral processes in mammals, including pain, sleep, feeding, and locomotor activity. Investigations into the structure and function of FAAH, its biological and therapeutic implications, as well as a description of different families of FAAH inhibitors are the topic of this review. [source] The tegument surface membranes of the human blood parasite Schistosoma mansoni: A proteomic analysis after differential extractionPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 5 2006Simon Braschi Abstract The blood fluke Schistosoma mansoni can live for years in the hepatic portal system of its human host and so must possess very effective mechanisms of immune evasion. The key to understanding how these operate lies in defining the molecular organisation of the exposed parasite surface. The adult worm is covered by a syncytial tegument, bounded externally by a plasma membrane and overlain by a laminate secretion, the membranocalyx. In order to determine the protein composition of this surface, the membranes were detached using a freeze/thaw technique and enriched by sucrose density gradient centrifugation. The resulting preparation was sequentially extracted with three reagents of increasing solubilising power. The extracts were separated by 2-DE and their protein constituents were identified by MS/MS, yielding predominantly cytosolic, cytoskeletal and membrane-associated proteins, respectively. After extraction, the final pellet containing membrane-spanning proteins was processed by liquid chromatographic techniques before MS. Transporters for sugars, amino acids, ions and other solutes were found together with membrane enzymes and proteins concerned with membrane structure. The proteins identified were categorised by their function and putative location on the basis of their homology with annotated proteins in other organisms. [source] | ||||||||||