The role of tryptophans on the cellular uptake and membrane interaction of arginine-rich cell penetrating peptides.

Cell-penetrating peptides (CPP) are able to efficiently transport cargos across cell membranes without being cytotoxic to cells, thus present a great potential in drug delivery and diagnosis. While the role of cationic residues in CPPs has been well studied, that of Trp is still not clear. Herein 7 peptide analogs of RW9 (RRWWRRWRR, an efficient CPP) were synthesized in which Trp were systematically replaced by Phe residues.

The colloidal state of tannins impacts the nature of their interaction with proteins: the case of salivary proline-rich protein/procyanidins binding.

While the definition of tannins has been historically associated with its propensity to bind proteins in a nonspecific way, it is now admitted that specific interaction also occurs. The case of the astringency perception is a good example to illustrate this phenomenon: astringency is commonly described as a tactile sensation induced by the precipitation of a complex composed of proline-rich proteins present in the human saliva and tannins present in beverages such as tea or red wines. In the present work, the interactions between a human saliva protein segment and three different procyanidins (B1, B3, and C2) were investigated at the atomic level by NMR and molecular dynamics.

Crystal structure and catalytic mechanism of leucoanthocyanidin reductase from Vitis vinifera.

Leucoanthocyanidin reductase (LAR) catalyzes the NADPH-dependent reduction of 2R,3S,4S-flavan-3,4-diols into 2R,3S-flavan-3-ols, a subfamily of flavonoids that is important for plant survival and for human nutrition. LAR1 from Vitis vinifera has been co-crystallized with or without NADPH and one of its natural products, (+)-catechin. Crystals diffract to a resolution between 1.

The epimerase activity of anthocyanidin reductase from Vitis vinifera and its regiospecific hydride transfers.

Anthocyanidin reductase (ANR) from Vitis vinifera catalyzes an NADPH-dependent double reduction of anthocyanidins producing a mixture of (2S,3R)- and (2S,3S)-flavan-3-ols. At pH 7.5 and 30 degrees C, the first hydride transfer to anthocyanidin is irreversible, and no intermediate is released during catalysis.

Structure and epimerase activity of anthocyanidin reductase from Vitis vinifera.

Together with leucoanthocyanidin reductase, anthocyanidin reductase (ANR) is one of the two enzymes of the flavonoid-biosynthesis pathway that produces the flavan-3-ol monomers required for the formation of proanthocyanidins or condensed tannins. It has been shown to catalyse the double reduction of anthocyanidins to form 2R,3R-flavan-3-ols, which can be further transformed to the 2S,3R isomers by non-enzymatic epimerization. ANR from grape (Vitis vinifera) was expressed in Escherichia coli and purified.

Reversible transition between alpha-helix and beta-sheet conformation of a transmembrane domain.

Despite the important functions of protein transmembrane domains, their structure and dynamics are often scarcely known. The SNARE proteins VAMP/synaptobrevin and syntaxin 1 are implicated in membrane fusion. Using different spectroscopic approaches we observed a marked sensitivity of their transmembrane domain structure in regard to the lipid/peptide ratio.

Structural evidence for the inhibition of grape dihydroflavonol 4-reductase by flavonols.

Dihydroflavonol 4-reductase (DFR) is a key enzyme of the flavonoid biosynthesis pathway which catalyses the NADPH-dependent reduction of 2R,3R-trans-dihydroflavonols to leucoanthocyanidins. The latter are the precursors of anthocyans and condensed tannins, two major classes of phenolic compounds that strongly influence the organoleptic properties of wine. DFR has been investigated in many plant species, but little was known about its structural properties until the three-dimensional structure of the Vitis vinifera enzyme complexed with NADP(+) and its natural substrate dihydroquercetin (DHQ) was described.

Peptide-presenting two-dimensional protein matrix on supported lipid bilayers: an efficient platform for cell adhesion.

Understanding and controlling cell adhesion to biomaterials and synthetic materials are important issues in basic research and applied sciences. Supported lipid bilayers (SLBs) functionalized with cell adhesion peptides linked to lipid molecules are popular platforms of cell adhesion. In this paper, an alternative approach of peptide presentation is presented in which peptides are stereo-selectively linked to proteins self-assembling in a rigid two-dimensional (2D) matrix on SLBs.

Variability in secondary structure of the antimicrobial peptide Cateslytin in powder, solution, DPC micelles and at the air-water interface.

Cateslytin (bCGA (344)RSMRLSFRARGYGFR(358)), a five positively charged 15 amino-acid residues arginine-rich antimicrobial peptide, was synthesized using a very efficient procedure leading to high yields and to a 99% purity as determined by HPLC and mass spectrometry. Circular dichroism, polarized attenuated total reflectance fourier transformed infrared, polarization modulation infrared reflection Absorption spectroscopies and proton two-dimensional NMR revealed the flexibility of such a peptide. Whereas being mostly disordered as a dry powder or in water solution, the peptide acquires a alpha-helical character in the "membrane mimicking" solvent trifuoroethanol.

Crystal structure of grape dihydroflavonol 4-reductase, a key enzyme in flavonoid biosynthesis.

The nicotinamide adenine dinucleotide phosphate (NADPH)-dependent enzyme dihydroflavonol 4-reductase (DFR) catalyzes a late step in the biosynthesis of anthocyanins and condensed tannins, two flavonoid classes of importance to plant survival and human nutrition. This enzyme has been widely investigated in many plant species, but little is known about its structural and biochemical properties. To provide a basis for detailed structure-function studies, the crystal structure of Vitis vinifera DFR, heterologously expressed in Escherichia coli, has been determined at 1.

Study of the yeast Saccharomyces cerevisiae F1F0-ATPase epsilon-subunit.

The yeast Saccharomyces cerevisiae F1F0-ATPase epsilon-subunit (61 residues) was synthesized by the solid-phase peptide approach under both acidic and basic strategies. Only the latter strategy allowed us to obtain a pure epsilon-subunit. The strong propensity of the protein to produce few soluble dimeric species depending on pH has been proved by size-exclusion chromatography, electrophoresis and mass spectrometry.