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Modeling of biological membranes in the study of tea flavonoids
Abstracts / Chemistry and Physics of Lipids 154S (2008) S21–S31
between two points measures the difference between two compositions. The model provides a general framework for comparison and visualization of lipidomics data.
S29
the PC species composition using ESI-MS/MS. Here we report on the comparison of the evolution of newly synthesized PC species between the pct1 knockout, the double knockout and the corresponding overexpression strain.
doi:10.1016/j.chemphyslip.2008.05.078 PO 26
Reference
Modeling of biological membranes in the study of tea flavonoids
Boumann, H.A., et al., 2003. The two biosynthetic routes leading to phosphatidylcholine in yeast produce different sets of molecular species. Evidence for lipid remodeling. Biochemistry 42, 3054–3059.
Timothy Sirk, Eugene Brown Mechanical Engineering Department, Virginia Tech, USA Experimental studies have shown that polyphenols found in tea can induce cell death in many bacteria and cancer cell lines. Although the process by which these compounds interact with cells remains unclear, it was recently suggested that the binding of a well-known tea polyphenol, (−)-epigallocatechin-gallate (EGCG), to the cell membrane plays a role in its antibacterial activity. To further explore the antibacterial and anticarcinogenic behavior of EGCG and other common tea polyphenols, we present molecular dynamics simulations to model the interactions of several bioactive tea polyphenols with the lipid bilayers of biological membranes. Specifically, 1-palmitoyl-2-oleoyl-snglycero-3-phosphocholine (POPC) lipid bilayers are exposed to an aqueous solution of flavonoid molecules. The nature of changes to the bilayer structure depend on bilayer-flavonoid interactions, such as the degree of hydrogen bonding of flavonoid hydroxyl groups and absorption/adsorption of the flavonoid into the bilayer. Our results provide insight into experimental results and give new details about the structural changes of lipid bilayers as a means to understand the biological activity of flavonoids found in tea. doi:10.1016/j.chemphyslip.2008.05.079 PO 27 Screening for yeast mutants disturbed in acyl chain remodeling of phosphatidyl choline Cedric De Smet 1 , Martin Houweling 2 , Jos Brouwers 2 , Toon de Kroon 1 1
Membrane Enzymology, Institute of Biomembranes and Bijvoet Institute, The Netherlands 2 Biochemistry and Cell Biology, Faculty of Veterinary Sciences, Utrecht University, The Netherlands Phosphatidylcholine (PC) is the major bilayer-forming phospholipid in eukaryotes and its species profile, i.e. the ensemble of PC molecules with acyl chains differing in length and saturation, is crucial for the fluidity and thickness of eukaryotic membranes. In S. cerevisiae, species-selective biosynthesis via the methylation of Phosphatidylethanoloamine (PE) and the CDP-choline route, and remodeling by acyl chain exchange, contribute to the PC species profile (Boumann et al., 2003). A pct1 deletion strain, in which the CDP-choline route is inactivated, obtains its steady state PC species profile by acyl chain remodeling of the PC pool synthesized by methylation of PE. Remodeling involves hydrolysis of one of the acyl chains by a phospholipase followed by a reacylation catalyzed by an acyl-CoA-dependent acyltransferase. Alternatively, remodeling could occur via transacylase-catalyzed reactions. In an extensive database search for enzymes that may catalyze these reactions, we identified 120 candidate genes. S. cerevisiae deletion strains for each of these genes were obtained and double mutants with an additional knockout of the PCT1 gene were produced. The 5 most promising ones were selected in a screen for
doi:10.1016/j.chemphyslip.2008.05.080 PO 28 Exogenous, heavy isotope-labeled species provide highly detailed information on phospholipids acyl chain remodeling Ville Kainu, Martin Hermansson, Pentti Somerharju Institute of Biomedicine, Department of Medial Biochemistry, University of Helsinki, Finland Mammalian cells maintain the phospholipid compositions of their different membranes remarkably constant. Beside de novo synthesis, degradation and intracellular trafficking, acyl chain remodeling plays a crucial role in phospholipid homeostasis, but many key details of this process remain unresolved due to methodological limitations. Recently, however, we have developed a novel approach that allows one to study metabolism of individual phospholipid species in unprecedented detail. In this approach exogenous, heavy isotope-labeled phospholipids are introduced to cells by cyclodextrin-mediated transfer and their metabolism is monitored by mass spectrometry [Kainu et al., 2008, J. Biol. Chem. 283, 3676–3687]. Studies with BHK21 and HeLa cells revealed that atypical (not pre-existing in cells) phosphatidylethanolamine (PE), -serine (PS) and -choline (PC) species were rapidly remodeled at the sn1 or sn2 position or both, eventually yielding a labeled species profile similar or identical to that the corresponding endogenous phospholipids. Consistently, exogenous species identical or similar to major endogenous ones were remodeled far less and at a much slower rate. Furthermore, major differences in remodeling pathways and kinetics were observed between species within a class (including acyl positional isomers), as well as between corresponding PE, PS and PC species. These data, along with those obtained with pharmacological inhibitors, indicate that multiple, remarkably specific A-type phospholipases and acyltransferases are involved in phospholipid remodeling. In conclusion, exogenous head-group labeled species provide highly detailed information on remodeling of glycerophospholipids and thus pave way for the elucidation of the specific phospholipases and acyltransferases/transacylases involved in phospholipid remodeling and phospholipid homeostasis in general. doi:10.1016/j.chemphyslip.2008.05.081 PO 29 Binding of antimicrobial peptides like plantaricin A, temporin B, and LL-37 to model biomembranes and their mode of action Rohit Sood, Paavo K.J. Kinnunen Helsinki Biophysics and Biomembrane Group, Medical Biochemistry, Institute of Biomedicine, P.O. Box 63 (Haartmaninkatu 8), University of Helsinki, FIN-00014 Helsinki, Finland Antimicrobial peptides (AMPs) constitute part of the non-adaptive host immunity providing a first line of defense against a wide
between two points measures the difference between two compositions. The model provides a general framework for comparison and visualization of lipidomics data.
S29
the PC species composition using ESI-MS/MS. Here we report on the comparison of the evolution of newly synthesized PC species between the pct1 knockout, the double knockout and the corresponding overexpression strain.
doi:10.1016/j.chemphyslip.2008.05.078 PO 26
Reference
Modeling of biological membranes in the study of tea flavonoids
Boumann, H.A., et al., 2003. The two biosynthetic routes leading to phosphatidylcholine in yeast produce different sets of molecular species. Evidence for lipid remodeling. Biochemistry 42, 3054–3059.
Timothy Sirk, Eugene Brown Mechanical Engineering Department, Virginia Tech, USA Experimental studies have shown that polyphenols found in tea can induce cell death in many bacteria and cancer cell lines. Although the process by which these compounds interact with cells remains unclear, it was recently suggested that the binding of a well-known tea polyphenol, (−)-epigallocatechin-gallate (EGCG), to the cell membrane plays a role in its antibacterial activity. To further explore the antibacterial and anticarcinogenic behavior of EGCG and other common tea polyphenols, we present molecular dynamics simulations to model the interactions of several bioactive tea polyphenols with the lipid bilayers of biological membranes. Specifically, 1-palmitoyl-2-oleoyl-snglycero-3-phosphocholine (POPC) lipid bilayers are exposed to an aqueous solution of flavonoid molecules. The nature of changes to the bilayer structure depend on bilayer-flavonoid interactions, such as the degree of hydrogen bonding of flavonoid hydroxyl groups and absorption/adsorption of the flavonoid into the bilayer. Our results provide insight into experimental results and give new details about the structural changes of lipid bilayers as a means to understand the biological activity of flavonoids found in tea. doi:10.1016/j.chemphyslip.2008.05.079 PO 27 Screening for yeast mutants disturbed in acyl chain remodeling of phosphatidyl choline Cedric De Smet 1 , Martin Houweling 2 , Jos Brouwers 2 , Toon de Kroon 1 1
Membrane Enzymology, Institute of Biomembranes and Bijvoet Institute, The Netherlands 2 Biochemistry and Cell Biology, Faculty of Veterinary Sciences, Utrecht University, The Netherlands Phosphatidylcholine (PC) is the major bilayer-forming phospholipid in eukaryotes and its species profile, i.e. the ensemble of PC molecules with acyl chains differing in length and saturation, is crucial for the fluidity and thickness of eukaryotic membranes. In S. cerevisiae, species-selective biosynthesis via the methylation of Phosphatidylethanoloamine (PE) and the CDP-choline route, and remodeling by acyl chain exchange, contribute to the PC species profile (Boumann et al., 2003). A pct1 deletion strain, in which the CDP-choline route is inactivated, obtains its steady state PC species profile by acyl chain remodeling of the PC pool synthesized by methylation of PE. Remodeling involves hydrolysis of one of the acyl chains by a phospholipase followed by a reacylation catalyzed by an acyl-CoA-dependent acyltransferase. Alternatively, remodeling could occur via transacylase-catalyzed reactions. In an extensive database search for enzymes that may catalyze these reactions, we identified 120 candidate genes. S. cerevisiae deletion strains for each of these genes were obtained and double mutants with an additional knockout of the PCT1 gene were produced. The 5 most promising ones were selected in a screen for
doi:10.1016/j.chemphyslip.2008.05.080 PO 28 Exogenous, heavy isotope-labeled species provide highly detailed information on phospholipids acyl chain remodeling Ville Kainu, Martin Hermansson, Pentti Somerharju Institute of Biomedicine, Department of Medial Biochemistry, University of Helsinki, Finland Mammalian cells maintain the phospholipid compositions of their different membranes remarkably constant. Beside de novo synthesis, degradation and intracellular trafficking, acyl chain remodeling plays a crucial role in phospholipid homeostasis, but many key details of this process remain unresolved due to methodological limitations. Recently, however, we have developed a novel approach that allows one to study metabolism of individual phospholipid species in unprecedented detail. In this approach exogenous, heavy isotope-labeled phospholipids are introduced to cells by cyclodextrin-mediated transfer and their metabolism is monitored by mass spectrometry [Kainu et al., 2008, J. Biol. Chem. 283, 3676–3687]. Studies with BHK21 and HeLa cells revealed that atypical (not pre-existing in cells) phosphatidylethanolamine (PE), -serine (PS) and -choline (PC) species were rapidly remodeled at the sn1 or sn2 position or both, eventually yielding a labeled species profile similar or identical to that the corresponding endogenous phospholipids. Consistently, exogenous species identical or similar to major endogenous ones were remodeled far less and at a much slower rate. Furthermore, major differences in remodeling pathways and kinetics were observed between species within a class (including acyl positional isomers), as well as between corresponding PE, PS and PC species. These data, along with those obtained with pharmacological inhibitors, indicate that multiple, remarkably specific A-type phospholipases and acyltransferases are involved in phospholipid remodeling. In conclusion, exogenous head-group labeled species provide highly detailed information on remodeling of glycerophospholipids and thus pave way for the elucidation of the specific phospholipases and acyltransferases/transacylases involved in phospholipid remodeling and phospholipid homeostasis in general. doi:10.1016/j.chemphyslip.2008.05.081 PO 29 Binding of antimicrobial peptides like plantaricin A, temporin B, and LL-37 to model biomembranes and their mode of action Rohit Sood, Paavo K.J. Kinnunen Helsinki Biophysics and Biomembrane Group, Medical Biochemistry, Institute of Biomedicine, P.O. Box 63 (Haartmaninkatu 8), University of Helsinki, FIN-00014 Helsinki, Finland Antimicrobial peptides (AMPs) constitute part of the non-adaptive host immunity providing a first line of defense against a wide