Tryptophan-lipid interactions in membrane protein folding probed by ultraviolet resonance Raman and fluorescence spectroscopy.

Aromatic amino acids of membrane proteins are enriched at the lipid-water interface. The role of tryptophan on the folding and stability of an integral membrane protein is investigated with ultraviolet resonance Raman and fluorescence spectroscopy. We investigate a model system, the β-barrel outer membrane protein A (OmpA), and focus on interfacial tryptophan residues oriented toward the lipid bilayer (trp-7, trp-170, or trp-15) or the interior of the β-barrel pore (trp-102).

Staphylococcus epidermidis antimicrobial delta-toxin (phenol-soluble modulin-gamma) cooperates with host antimicrobial peptides to kill group A Streptococcus.

Antimicrobial peptides play an important role in host defense against pathogens. Recently, phenol-soluble modulins (PSMs) from Staphylococcus epidermidis (S. epidermidis) were shown to interact with lipid membranes, form complexes, and exert antimicrobial activity.

Förster Resonance Energy Transfer and Conformational Stability of Proteins: An Advanced Biophysical Module for Physical Chemistry Students.

Protein folding is an exploding area of research in biophysics and physical chemistry. Here, we describe the integration of several techniques, including absorption spectroscopy, fluorescence spectroscopy, and Förster resonance energy transfer (FRET) measurements, to probe important topics in protein folding. Cytochrome c is used as a model protein; comparison of conformational stabilities ( ΔGH2O∘) measured via two chemical denaturants, urea and guanidinium hydrochloride, illustrate important concepts in protein folding and intermolecular interactions.

Selective antimicrobial action is provided by phenol-soluble modulins derived from Staphylococcus epidermidis, a normal resident of the skin.

Antimicrobial peptides serve as a first line of innate immune defense against invading organisms such as bacteria and viruses. In this study, we hypothesized that peptides produced by a normal microbial resident of human skin, Staphylococcus epidermidis, might also act as an antimicrobial shield and contribute to normal defense at the epidermal interface. We show by circular dichroism and tryptophan spectroscopy that phenol-soluble modulins (PSMs) gamma and delta produced by S.

Effects of tryptophan microenvironment, soluble domain, and vesicle size on the thermodynamics of membrane protein folding: lessons from the transmembrane protein OmpA.

Refolding curves of the integral membrane protein outer membrane protein A (OmpA) were measured to determine the conformational stabilities of this model system for membrane protein folding. Wild-type OmpA exhibits a free energy of unfolding (DeltaG degrees H2O) of 10.5 kcal/mol.

Ultraviolet resonance Raman spectroscopy of folded and unfolded states of an integral membrane protein.

The vibrational structure of native anchoring tryptophan (Trp) and tyrosine residues in an integral membrane protein, bacterial outer membrane protein A (OmpA), have been investigated using UV resonance Raman (UVRR) spectroscopy for the first time. Spectra of native OmpA, a single-Trp mutant, and a Trp-less mutant were recorded in folded and unfolded states, and reveal significant changes in tryptophan structure and local environment. Salient alterations upon folding include loss of hydrogen-bonding character of indole N1H, evidenced by a shift in W17 frequency from 874 and 878 cm(-1), and growth in hydrophobicity of the local tryptophan environment, supported by increase in the ratio I1361/I1340.