Structure of Phospholipid Mixed Micelles (Bicelles) Studied by Small-Angle X-ray Scattering.

Mixed phospholipid micelles (bicelles) are widely applied in nuclear magnetic resonance (NMR) studies of membrane proteins in solution, as they can solubilize these proteins and provide a membrane-like environment. In this work, the structure of bicelles of dihexanoyl phosphatidyl choline (DHPC) and dimyristoyl phosphatidyl choline (DMPC) at different ratios was determined by small-angle X-ray scattering (SAXS) at 37 °C. Samples with concentrations as applied for NMR measurements with 28 wt % lipids were diluted to avoid concentration effects in the SAXS data.

How a short pore forming peptide spans the lipid membrane.

Many antimicrobial peptides function by forming pores in the plasma membrane of the target cells. Intriguingly, some of these peptides are very short, and thus, it is not known how they can span the membrane, or whether other mechanisms of cell disruption are dominant. Here, the conformation and orientation of the 14-residue peptaibol SPF-5506-A (SPF) are investigated in lipid environments by atomistic and coarse grained molecular dynamics (MD) simulations, circular dichroism, and nuclear magnetic resonance (NMR) experiments.

Solid-state NMR methods for oriented membrane proteins.

Oriented-sample solid-state NMR represents one of few experimental methods capable of characterising the membrane-bound conformation of proteins in the cell membrane. Since the technique was developed 25 years ago, the technique has been applied to study the structure of helix bundle membrane proteins and antimicrobial peptides, characterise protein-lipid interactions, and derive information on dynamics of the membrane anchoring of membrane proteins. We will review the major developments in various aspects of oriented-sample solid-state NMR, including sample-preparation methods, pulse sequences, theory required to interpret the experiments, perspectives for and guidelines to new experiments, and a number of representative applications.

The natural, peptaibolic peptide SPF-5506-A4 adopts a β-bend spiral structure, shows low hemolytic activity and targets membranes through formation of large pores.

The medium-length fungal peptaibol SPF-5506-A(4) has been shown to inhibit formation of the Aβ peptide involved in Alzheimer''s disease. As Aβ is a cleavage-product from the membrane-bound APP protein, we hypothesized that SPF-5506-A(4)'s activity might be linked to membrane interactions in general. Here we describe the synthesis, structure and membrane interactions of SPF-5506-A4.

Lipid dynamics studied by calculation of 31P solid-state NMR spectra using ensembles from molecular dynamics simulations.

We present a method to calculate (31)P solid-state NMR spectra based on the dynamic input from extended molecular dynamics (MD) simulations. The dynamic information confered by MD simulations is much more comprehensive than the information provided by traditional NMR dynamics models based on, for example, order parameters. Therefore, valuable insight into the dynamics of biomolecules may be achieved by the present method.

Mechanisms of peptide-induced pore formation in lipid bilayers investigated by oriented 31P solid-state NMR spectroscopy.

There is a considerable interest in understanding the function of antimicrobial peptides (AMPs), but the details of their mode of action is not fully understood. This motivates extensive efforts in determining structural and mechanistic parameters for AMP's interaction with lipid membranes. In this study we show that oriented-sample (31)P solid-state NMR spectroscopy can be used to probe the membrane perturbations and disruption by AMPs.

Long-term-stable ether-lipid vs conventional ester-lipid bicelles in oriented solid-state NMR: altered structural information in studies of antimicrobial peptides.

Recently, ether lipids have been introduced as long-term stable alternatives to the more natural, albeit easier degradable, ester lipids in the preparation of oriented lipid bilayers and bicelles for oriented-sample solid-state NMR spectroscopy. Here we report that ether lipids such as the frequently used 14-O-PC (1,2-di-O-tetradecyl-sn-glycero-3-phosphocholine) may induce significant changes in the structure and dynamics, including altered interaction between peptides and lipids relative to what is observed with the more conventionally used DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) bilayers. Such effects are demonstrated for the antimicrobial peptide novicidin, for which 2D separate-local-field NMR and circular dichroism experiments reveal significant structural/conformational differences for the peptide in the two different lipid systems.

Analysis of separate and combined effects of common variation in KCNJ11 and PPARG on risk of type 2 diabetes.

The separate and combined effects of the PPARG Pro(12)Ala polymorphism and the KCNJ11 Glu(23)Lys polymorphisms on risk of type 2 diabetes were investigated in relatively large-scale, case-control studies. Separate effects of the variants were examined among 1187/1461 type 2 diabetic patients and 4791/4986 middle-aged, glucose-tolerant subjects. The combined analysis involved 1164 type 2 diabetic patients and 4733 middle-aged, glucose-tolerant subjects.

PGC-1alpha Gly482Ser polymorphism associates with hypertension among Danish whites.

PGC-1alpha is a coactivator of numerous transcription factors and is expressed in tissues with high energy demands and abundant in mitochondria. It is induced in the myocardium on fasting and physical exercise, and cardiac-specific overexpression stimulates mitochondrial biogenesis in mice. The common Gly482Ser polymorphism of PGC-1alpha has previously shown association with arterial hypertension among Austrian men.

Genetic evidence that HNF-1alpha-dependent transcriptional control of HNF-4alpha is essential for human pancreatic beta cell function.

Mutations in the genes encoding hepatocyte nuclear factor 4alpha (HNF-4alpha) and HNF-1alpha impair insulin secretion and cause maturity onset diabetes of the young (MODY). HNF-4alpha is known to be an essential positive regulator of HNF-1alpha. More recent data demonstrates that HNF-4alpha expression is dependent on HNF-1alpha in mouse pancreatic islets and exocrine cells.