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Molecular dynamics simulation studies of lipid bilayer systems.

100%

Pasenkiewicz-Gierula M. , Murzyn K. , Róg T. , Czaplewski C.

nr 3

601-611

The main structural element of biological membranes is a liquid-crystalline lipid bilayer. Other constituents, i.e. proteins, sterols and peptides, either intercalate into or loosely attach to the bilayer. We applied a molecular dynamics simulation method to study membrane systems at various levels of compositional complexity. The studies were started from simple lipid bilayers containing a single type phosphatidylcholine (PC) and water molecules (PC bilayers). As a next step, cholesterol (Chol) molecules were introduced to the PC bilayers (PC-Chol bilayers). These studies provided detailed information about the structure and dynamics of the membrane/water interface and the hydrocarbon chain region in bilayers built of various types of PCs and Chol. This enabled studies of membrane systems of higher complexity. They included the investigation of an integral membrane protein in its natural environment of a PC bilayer, and the antibacterial activity of magainin-2. The latter study required the construction of a model bacterial membrane which consisted of two types of phospholipids and counter ions. Whenever published experimental data were available, the results of the simulations were compared with them.

Interaction of spectrin with phospholipids is inhibited by isolated erythrocyte ankyrin. A monolayer study

84%

Bialkowska K. , Lesniewski J. , Nietubyc M. , Sikorski A. F.

Cellular and Molecular Biology Letters

1999

tom 04

nr 2

It was previously found (Białkowska, K., Zembroń, A. and Sikorski, A. F. (1994) Biochim. Biophys. Acta 1191, 21-26.) that isolated erythrocyte ankyrin inhibited interaction of spectrin with phospholipid liposomes, mainly those prepared from lipid mixtures containing aminophospholipids. In this communication we report on the effect of isolated ankyrin on red blood cell spectrin interaction with phospholipids in monolayers. Our data indicate that spectrin interaction with monolayers containing PE and, to a smaller extent, PS is sensitive to inhibition by ankyrin while interaction with monolayers containing only PC is not. Tetrameric spectrin affects monolayer surface pressure similarly to the heterodimer. However, an interaction of tetrameric spectrin with phospholipids was much more effectively inhibited by purified ankyrin indicating that one site per spectrin tetramer engaged in this interaction. When interactions of purified individual spectrin subunits (α or β) with phospholipid monolayers was studied, the β-subunit caused a strong, saturable effect on the surface pressure of the PE/PC monolayer, in contrast to the α-chain which induced much smaller and monotonic changes on the surface pressure of the same monolayer. Also interactions of the β-subunit with amino-phospholipids/PC monolayers were more sensitive to inhibition by ankyrin than those with native αβ-heterodimer of spectrin, e.g. threefold lower concentration of ankyrin was necessary to induce the same effect, while interaction of the α-subunit with phospholipid monolayers was entirely insensitive to ankyrin. Phosphorylation of spectrin in vitro with either cAMP-dependent protein kinase, or metabolically in intact cells, induced a decrease in the effect of either dimer or tetramer on the surface pressure of phospholipid monolayers. The sensitivity of this interaction to ankyrin was also greatly diminished. When isolated ankyrin was phosphorylated by the same cAMP-dependent protein kinase its ability to compete with phospholipid for spectrin was also diminished. The described effects may indicate a physiological significance of spectrin’s interaction with phospholipids, particularly in situations when there is not enough functional ankyrin to accommodate all spectrin molecules in the membrane.

Evidence for the presence of the Kennedy and Bremer-Greenberg pathways in Caenorhabditis elegans

67%

Lochnit G. , Heyer R.

nr 4

Nematodes were found to synthesize phosphorylcholine-containing molecules not present in higher organisms, i.e. phosphorylcholine-substituted glycosphingolipids and (glyco)proteins. Investigations on the biosynthesis of these structures provided first biochemical evidence for the presence of the Kennedy and Bremer-Greenberg pathways in the model organism Caenorhabditis elegans.

Effect of triiodothyronine on the content of phospholipids in the rat liver nuclei

67%

Bucki R. , Gorska M. , Zendzian-Piotrowska M. , Gorski J.

nr 3

Prostaglandin E [dmPGE2] action in vitro on the activity of rat liver Golgi apparatus galactosyltransferase

67%

Kordowiak A. M. , Tomecki J. , Procyk K. , Kapusta P.

tom 40

nr 4

In vitro addition of 16,16'-dimethyl prostaglandin E2 to Golgi-rich membrane fraction in final concentration of 0.1 ng/1 mg of protein increased generally the activity of galactosyltransferase in comparison with control. The percentage of phospholipids in the whole fraction was similar in both investigated groups, only the sum of phosphatidylethanolamine + phosphatide acid was significantly lower after addition of dmPGE2 than in the control (0.001

Temporal dynamics and regional distribution of [14 C] serine uptake into mouse brain

59%

Woronczak J. P. , Siucinska E. , Kossut M. , Baranska J.

Acta Neurobiologiae Experimentalis

1995

tom 55

nr 4