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Leu Residues (leu + residue)
Selected AbstractsHybrid ,/,3 -peptides with proteinogenic side chains. monosubstituted analogues of the chemotactic tripeptide For-Met-Leu-Phe-OMeJOURNAL OF PEPTIDE SCIENCE, Issue 8 2004Cesare Giordano Abstract The ,/,3 -mixed tripeptides R-CO-,3 -HMet-Leu-Phe-OMe (1a,b), R-CO-Met-,3 -HLeu-Phe-OMe (2a,b) and R-CO-Met-Leu-,3 -HPhe-OMe (3a,b) (a, R = tert -butyloxy-; b, R = H,), analogues of the potent chemoattractant For-Met-Leu-Phe-OMe, have been synthesized by classical solution methods and fully characterized. The activities of the new analogues as chemoattractants, superoxide anion producers and lysozyme releasers have been determined on human neutrophils. Whereas all of the three N -formyl derivatives are significantly less active than the parent tripeptide as chemoattractants, compound 1b has been found to be highly active as a superoxide anion producer and 3b as a lysozyme releaser. The results show that the replacement of the native Leu residue at the central position is, in each of the examined cases, the least favourable modification. The three N -Boc derivatives are, as expected, devoid of activity as agonists, but they are all good inhibitors of chemotaxis. Information on the solution conformation has been obtained by examining the involvement of the NH groups in intramolecular H-bonds using 1H NMR. The conformation of the N -Boc analogue 1a has also been determined in the crystal state by x-ray diffraction analysis. The molecule is extended at the ,3 -HMet residue (,1 = ,87°;,1 = 172°;,1 = 126° ) and no intramolecular H-bond is present. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd. [source] Chiral interaction in peptide molecules: Effects of chiral peptide species on helix-sense induction in an N-terminal-free achiral peptideBIOPOLYMERS, Issue 5 2006Yoshihito Inai Abstract Noncovalent chiral domino effect (NCDE) has been proposed as terminal-specific interaction upon a 310 -helical peptide chain, of which the helix sense is manipulated by an external chiral stimulus (mainly amino acid derivatives) operating on the N-terminus (Inai, Y., et al. J Am Chem Soc 2000, 122, 11731,11732; ibid., 2002, 124, 2466,2473; ibid., 2003, 125, 8151,8162). We have investigated here a helix-sense induction in an optically inactive N-terminal-free nonapeptide (1) through the screening of several peptide species that differ in chiral sequence, chain length, and C-terminal group. Helix-sense induction in peptide 1 depends largely on both the C-terminal chirality and carboxyl group in the external peptide, in which N-carbonyl-blocked amino acids, "monopeptide acids," should be the minimum requirement for effective induction. N-Protected mono- to tetrapeptides of L -Leu residue commonly induce a right-handed helix. NMR study and theoretical computation reveal that the N-terminal segment of peptide 1 binds the N-protected dipeptide molecule through multipoint coordination to induce a right-handed helix preferentially. The present findings not only will improve our understanding of the chiral roles in peptide or protein helical termini, but also might demonstrate potential applications to chirality-responsive materials based on peptide helical fragments. © 2006 Wiley Periodicals, Inc. Biopolymers 82: 471,481, 2006 This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] A novel prohormone processing site in Aplysia californica: the Leu,Leu ruleJOURNAL OF NEUROCHEMISTRY, Issue 6 2002Amanda B. Hummon Abstract Neuropeptides are a complex set of signaling molecules produced through enzymatic cleavages from longer prohormone sequences. The most common cleavage sites in prohormones are basic amino acid residues; however, processing is observed at non-basic sites. Cleavage at Leu,Leu sequences has been observed in three Aplysia californica prohormones. To further investigate this unusual event, native and non-native synthetic peptides containing Leu,Leu residues are incubated with homogenates of Aplysia californica ganglia and the resulting products monitored with MALDI MS. Cleavage near and between Leu,Leu residues is observed in the abdominal and buccal ganglia homogenates, confirming the presence of an unidentified peptidase. In addition, fractions from an HPLC separation of buccal ganglia homogenates also produce cleavages at Leu,Leu residues. Products resulting from cleavage at Leu,Leu sites are observed and are produced in larger amounts in acidic and neutral pH ranges, and cleavage is inhibited by the addition of EDTA, suggesting a metal is required for activity. [source] Role of the transmembrane domain of glycoprotein IX in assembly of the glycoprotein Ib,IX complexJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 12 2007S.-Z. LUO Summary.,Background:,The glycoprotein (GP) Ib,IX complex is critically involved in platelet adhesion to von Willebrand factor and in the initial step of platelet activation. How this complex is assembled is not clear. We previously showed that the transmembrane (TM) domains of the GPIb, and GPIb, subunits interact and participate in complex assembly. Objectives and methods:,Here, we have investigated the role of the TM and cytoplasmic domains of GPIX in assembly of the GPIb,IX complex, by analyzing the mutational effects on complex expression and assembly in transiently transfected Chinese hamster ovary cells. Results:,Replacing the cytoplasmic domain of GPIX with a poly-alanine sequence had little effect on surface expression and structural integrity of the GPIb,IX complex. In contrast, replacing the GPIX TM domain (residues 132,153) with a poly-leucine-alanine sequence markedly disrupted complex formation of GPIX with GPIb,, interfered with GPIb formation, and decreased surface expression of the host complex. We further analyzed the contributions of a number of GPIX TM residues to complex formation by mutagenesis and found significant roles for Asp135 and several Leu residues. Conclusions:,The TM domain, rather than the cytoplasmic domain, of GPIX plays an important role in expression and assembly of the GPIb,IX complex by interacting with its counterparts of GPIb. These TM domains may form a parallel four-helical bundle structure in the complex. [source] RNA Grooves Can Accommodate Disulfide-Bridged Bundles of ,-Helical PeptidesCHEMBIOCHEM, Issue 6 2010Soonsil Hyun Dr. Feelin' groovy: A strategy for chemical stapling increases structural as well as chemical stability of helical peptides. Using an amphiphilic peptide with Leu/Lys, two Leu residues were replaced by Cys. Helical bundle peptides were generated by oxidative disulfide bond formation. One of these has a Kd as low as 21 pM against hairpin targets. This observation demonstrates that the groove in small hairpin RNA has sufficient room to contain a helical bundle peptide. [source] | ||||||||||