Self-association of unfolded outer membrane proteins.

We have investigated self-association propensities of aqueous unfolded (U(AQ)) forms of eight outer membrane proteins (OMPs), OmpA, OmpW, OmpX, PagP, OmpT, OmpLa, FadL, and Omp85. We found that high urea concentrations maintain all of these OMPs as monomers and that OmpA and OmpX remain monomeric upon dilution to 1 M urea. A pH screen showed that basic pH supports the least amount of U(AQ) OMP self-association, consistent with earlier studies showing that basic pH was optimal for better folding efficiencies.

Beta-barrel proteins that reside in the Escherichia coli outer membrane in vivo demonstrate varied folding behavior in vitro.

Little is known about the dynamic process of membrane protein folding, and few models exist to explore it. In this study we doubled the number of Escherichia coli outer membrane proteins (OMPs) for which folding into lipid bilayers has been systematically investigated. We cloned, expressed, and folded nine OMPs: outer membrane protein X (OmpX), OmpW, OmpA, the crcA gene product (PagP), OmpT, outer membrane phospholipase A (OmpLa), the fadl gene product (FadL), the yaet gene product (Omp85), and OmpF.

Determination of membrane protein molecular weights and association equilibrium constants using sedimentation equilibrium and sedimentation velocity.

Regulated molecular interactions are essential for cellular function and viability, and both homo- and hetero-interactions between all types of biomolecules play important cellular roles. This chapter focuses on interactions between membrane proteins. Knowing both the stoichiometries and stabilities of these interactions in hydrophobic environments is a prerequisite for understanding how this class of proteins regulates cellular activities in membranes.

Hyperserotoninemia and altered immunity in autism.

One of the most consistent biological findings in autism is elevated whole blood serotonin (5-HT) levels found in about 1/3 of cases. Immune abnormalities are also commonly observed in this disorder. Given 5-HT's role as an immunomodulator, possible connections between 5-HT and immune abnormalities in autism are explored in this review.

Mechanisms governing the level of susceptibility of erythrocyte membranes to secretory phospholipase A2.

Although cell membranes normally resist the hydrolytic action of secretory phospholipase A(2) (sPLA(2)), they become susceptible during apoptosis or after cellular trauma. Experimentally, susceptibility to the enzyme can be induced by loading cells with calcium. In human erythrocytes, the ability of the calcium ionophore to cause susceptibility depends on temperature, occurring best above approximately 35 degrees C.