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How lipids influence the mode of action of membrane-activ e peptides: Biochimica et Biophysica Acta (BBA) - Biomembranes, Vol. 1768, No. 10. (October 2007), pp. 2586-2595.The human, multifunctiona l peptide LL-37 causes membrane disruption by distinctly different mechanisms strongly dependent on the nature of the membrane lipid composition, varying not only with lipid headgroup charge but also with hydrocarbon chain length. Specifically, LL-37 induces a peptide-associ ated quasi-interdig itated phase in negatively charged phosphatidylgl ycerol (PG) model membranes, where the hydrocarbon chains are shielded from water by the peptide. In turn, LL-37 leads to a disintegration of the lamellar organization of zwitterionic dipalmitoyl-ph osphatidylchol ine (DPPC) into disk-like micelles. Interestingly, interdigitatio n was also observed for the longer-chain C18 and C20 PCs. This dual behavior of LL-37 can be attributed to a balance between electrostatic interactions reflected in different penetration depths of the peptide and hydrocarbon chain length. Thus, our observations indicate that there is a tight coupling between the peptide properties and those of the lipid bilayer, which needs to be considered in studies of lipid/peptide interaction. Very similar effects were also observed for melittin and the frog skin peptide PGLa. Therefore, we propose a phase diagram showing different lipid/peptide arrangements as a function of hydrocarbon chain length and LL-37 concentration and suggest that this phase diagram is generally applicable to membrane-activ e peptides localized parallel to the membrane surface.E Sevcsik, G Pabst, A Jilek, K Lohner

Source: Biochimica et Biophysica Acta (BBA) - Biomembranes, Vol. 1768, No. 10. (October 2007), pp. 2586-2595.
Lipid domains in bacterial membranes: Molecular Microbiology, Vol. 61, No. 5. (September 2006), pp. 1110-1117.Mats umoto, Kouji, Kusaka, Jin, Nishibori, Ayako, Hara, Hiroshi

Source: Molecular Microbiology, Vol. 61, No. 5. (September 2006), pp. 1110-1117.
Zwitterionic Phospholipids and Sterols Modulate Antimicrobial Peptide-Induce d Membrane Destabilizatio n: Biophys. J., Vol. 93, No. 12. (15 December 2007), pp. 4289-4299.Cati onic amphipathicalp ha -helical peptides preferentially disrupt anionic lipids in mixed model membranes, potentially causing a catastrophic release of the cell contents or attenuation of the membrane potential. The effective role of such peptides requires considerable discrimination between target and host cells, which is likely to occur at the level of the cell membrane. Here, we explore the roles of a variety of common membrane constituents in mediating the interaction between the antimicrobial peptide pleurocidin and model membranes. We employ intrinsic tryptophan fluorescence and circular dichroism to observe the effect of increasing concentrations of sterol in the membrane on peptide binding, using 2H solid-state NMR of chain deuterated lipids simultaneously to probe the effective chain disruption of the anionic phospholipid component of the membrane. We show that the degree of ordering of the lipid acyl chains in the membrane is dependent on the nature of the zwitterionic phospholipid headgroup in mixed anionic membranes. Furthermore, the presence of cholesterol and ergosterol increases acyl chain order in the liquid crystalline model membranes, but to differing degrees. Our results show how sterols can protect even negatively charged membranes from the disruptive effects of antimicrobial peptides, thereby providing a molecular view of the differences in sensitivity of various target membranes to linear cationic antibiotic peptides where bacteria (no sterols) are most susceptible, lower eukaryotes including fungi (containing ergosterol) exhibit an intermediate degree of sensitivity, and higher organisms (containing cholesterol) are largely resistant to antimicrobial peptides. 10.1529/biophy sj.107.116681J ames Mason, Arnaud Marquette, Burkhard Bechinger

Source: Biophys. J., Vol. 93, No. 12. (15 December 2007), pp. 4289-4299.
Skeletal muscle metabolic dysfunction in obesity and metabolic syndrome.: The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques, Vol. 35, No. 1. (March 2008), pp. 31-40.Obesity and the related metabolic syndrome have become a worldwide epidemic. Inactivity appears to be a primary causative factor in the pathogenesis of this obesity and metabolic syndrome. There are two possible, perhaps not mutually exclusive, events that may lead to intramyocellul ar lipid accumulation and mitochondrial dysfunction in patients with obesity. First, obesity, with high intake-associa ted lipid accumulation in muscle may interfere with cellular mitochondrial function through generation of reactive oxygen species leading to lipid membrane peroxidative injury and disruption of mitochondrial membrane-depen dent enzymes. This in turn leads to impaired oxidative metabolism. Secondly, a primary defect in mitochondrial oxidative metabolism may be responsible for a reduction in fatty acid oxidation leading to intramyocellul ar lipid accumulation as a secondary event. Non-invasive techniques such as proton (1H) and phosphorus (31P) magnetic resonance spectroscopy, coupled with specific magnetic resonance imaging techniques, may facilitate the investigation of the effects of various ergometric interventions on the pathophysiolog y of obesity and the metabolic syndrome. Exercise has positive effects on glucose metabolism, aerobic metabolism, mitochondrial density, and respiratory chain proteins in patients with metabolic syndrome, and we propose that this may be due to the exercise effects on AMP kinase, and a prospective physiological mechanism for this benefit is presented. A physiological model of the effect of intramyocellul ar lipid accumulation on oxidative metabolism and insulin mediated glucose uptake is proposed.GD Wells, MD Noseworthy, J Hamilton, M Tarnopolski, I Tein

Source: The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques, Vol. 35, No. 1. (March 2008), pp. 31-40.
Modulation of adenosine 5?-monophospha te adsorption onto aqueous resident pyrite: Potential mechanisms for prebiotic reactions: Origigins of Life and Evolution of the Biosphere, Vol. 31, No. 4-5. (2001), pp. 343-362.The adsorption of adenosine 5?-monophospha te (5?-AMP) onto pyrite (FeS2) and its modulation by acetate, an organic precursor of complex metabolic pathways, was studied in aqueous media that simulate primitive environments. 5?-AMP adsorption requires divalent cations, indicating that a cationic bridge mediates its attachment to negatively charged sites of the mineral surface. The isotherm of 5?-AMP adsorption exhibits a strong cooperative effect at low nucleotide concentrations in acetate-rich medium, whereas high levels of adsorption were only found at high nucleotide concentrations in a model of primitive seawater (acetate free). The modulating role of acetate is also evidenced in the presence of high dipolar moment molecules: dimethyl sulfoxide (Me2SO) and dimethyl formamide (DMF) strongly inhibit 5?-AMP adsorption in acetate-rich media, whereas no effect of DMF was found in artificial seawater. The observation that exogenous divalent cations are not needed for acetate attachment onto FeS2 reveals that organic acids can interact with the Fe2+ atoms in the mineral surface. All considered, the results show that complex and flexible iron-sulfide/b iomonomers interactions can be modulated by molecules that accumulate in the interface layer.M Pontes-Buarque s, AC Tessis, JAP Bonapace, MBM Monte, G Corte?s-Lopez, F De Souza-Barros, A Vieyra

Source: Origigins of Life and Evolution of the Biosphere, Vol. 31, No. 4-5. (2001), pp. 343-362.
Bactericidal/p ermeability-in creasing protein (BPI) and BPI homologs at mucosal sites: Trends in Immunology, Vol. 29, No. 11. (November 2008), pp. 541-547.G Canny, O Levy

Source: Trends in Immunology, Vol. 29, No. 11. (November 2008), pp. 541-547.
Hypoxia and AMP independently regulate AMP-activated protein kinase activity in heart.: Am J Physiol Heart Circ Physiol, Vol. 288, No. 5. (May 2005)The hypothesis was tested that hypoxia increases AMP-activated protein kinase (AMPK) activity independently of AMP concentration ([AMP]) in heart. In isolated perfused rat hearts, cytosolic [AMP] was changed from 0.2 to 16 microM using metabolic inhibitors during both normal oxygenation (95% O2-5% CO2, normoxia) and limited oxygenation (95% N2-5% CO2, hypoxia). Total AMPK activity measured in vitro ranged from 2 to 40 pmol.min(-1).m g protein(-1) in normoxic hearts and from 5 to 55 pmol.min(-1).m g protein(-1) in hypoxic hearts. The dependence of the in vitro total AMPK activity on the in vivo cytosolic [AMP] was determined by fitting the measurements from individual hearts to a hyperbolic equation. The [AMP] resulting in half-maximal total AMPK activity (A0.5) was 3 +/- 1 microM for hypoxic hearts and 28 +/- 13 microM for normoxic hearts. The A0.5 for alpha2-isoform AMPK activity was 2 +/- 1 microM for hypoxic hearts and 13 +/- 8 microM for normoxic hearts. Total AMPK activity correlated with the phosphorylatio n of the Thr172 residue of the AMPK alpha-subunit. In potassium-arre sted hearts perfused with variable O2 content, alpha-subunit Thr172 phosphorylatio n increased at O2 < or = 21% even though [AMP] was

Source: Am J Physiol Heart Circ Physiol, Vol. 288, No. 5. (May 2005)
Recognition of antimicrobial peptides by a bacterial sensor kinase.: Cell, Vol. 122, No. 3. (12 August 2005), pp. 461-472.PhoQ is a membrane bound sensor kinase important for the pathogenesis of a number of Gram-negative bacterial species. PhoQ and its cognate response regulator PhoP constitute a signal-transdu ction cascade that controls inducible resistance to host antimicrobial peptides. We show that enzymatic activity of Salmonella typhimurium PhoQ is directly activated by antimicrobial peptides. A highly acidic surface of the PhoQ sensor domain participates in both divalent-catio n and antimicrobial- peptide binding as a first step in signal transduction across the bacterial membrane. Identification of PhoQ signaling mutants, binding studies with the PhoQ sensor domain, and structural analysis of this domain can be incorporated into a model in which antimicrobial peptides displace divalent cations from PhoQ metal binding sites to initiate signal transduction. Our findings reveal a molecular mechanism by which bacteria sense small innate immune molecules to initiate a transcriptiona l program that promotes bacterial virulence.MW Bader, S Sanowar, ME Daley, AR Schneider, U Cho, W Xu, RE Klevit, H Le Moual, SI Miller

Source: Cell, Vol. 122, No. 3. (12 August 2005), pp. 461-472.
Antibacterial peptides: basic facts and emerging concepts.: J Intern Med, Vol. 254, No. 3. (September 2003), pp. 197-215.Antiba cterial peptides are the effector molecules of innate immunity. Generally they contain 15-45 amino acid residues and the net charge is positive. The cecropin type of linear peptides without cysteine were found first in insects, whilst the defensin type with three disulphide bridges were found in rabbit granulocytes. Now a database stores more than 800 sequences of antibacterial peptides and proteins from the animal and plant kingdoms. Generally, each species has 15-40 peptides made from genes, which code for only one precursor. The dominating targets are bacterial membranes and the killing reaction must be faster than the growth rate of the bacteria. Some antibacterial peptides are clearly multifunctiona l and an attempt to predict this property from the hydrophobicity of all amino acid side chains are given. Gene structures and biosynthesis are known both in the fruit fly Drosophila and several mammals. Humans need two classes of defensins and the cathelicidin-d erived linear peptide LL-37. Clinical cases show that deficiencies in these peptides give severe symptoms. Examples given are morbus Kostmann and atopic allergy. Several antibacterial peptides are being developed as drugs.HG Boman

Source: J Intern Med, Vol. 254, No. 3. (September 2003), pp. 197-215.
Small cationic protein from a marine turtle has beta-defensin- like fold and antibacterial and antiviral activity.: Proteins (12 May 2006)Egg white of marine turtle Caretta caretta contains a small cationic protein but lacks lysozyme. The protein was sequenced by a combination of sequential Edman degradation, carboxypeptida se digestion, nuclear magnetic resonance (NMR) and electrospray ionization tandem mass spectrometry. The protein contains 36 amino acid residues of which six are half-cysteines . The three-dimensio nal structure of the protein was deduced from two-dimensiona l NMR experiments and was observed to be similar to vertebrate beta-defensins . However, disulfide connectivity is C1-C6/C2-C5/C3 -C4; different from that of the vertebrate beta-defensins . The protein showed strong antibacterial activity against Escherichia coli and Salmonella typhimurium. The protein also showed significant antiviral activity against an enveloped rhabdovirus, Chandipura virus, which is an emerging human pathogen. This virus is also closely related to the vesicular stomatitis virus, whose growth was also inhibited. This small cationic protein is part of the innate immunity of this organism and replaces lysozyme in the egg. It has the potential to be developed as an antibacterial and antiviral agent. Proteins 2006. (c) 2006 Wiley-Liss, Inc.Suranjana Chattopadhyay, Nirmal Kumar Sinha, Shuvojit Banerjee, Debjani Roy, Dhrubajyoti Chattopadhyay, Siddhartha Roy

Source: Proteins (12 May 2006)

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