Detailed characterization of cysteine-less P-glycoprotein reveals subtle pharmacological differences in function from wild-type protein.

1. Subtle alterations in the coupling of drug binding to nucleotide hydrolysis were observed following mutation of all seven endogenous cysteine residues to serines in the human multidrug resistance transporter, P-glycoprotein. Wild-type (wt) and the mutant (cys-less) forms of P-gp were expressed in Trichoplusia ni (High Five) cells and purified by metal affinity chromatography in order to undertake functional studies.

The importance of cholesterol in maintenance of P-glycoprotein activity and its membrane perturbing influence.

In tumour cell lines that display multidrug resistance, expression of P-glycoprotein (P-gp) alters many aspects of biomembrane organization in addition to its well-characterized drug transport activity. We have developed a reconstitution system to directly investigate the effect of purified P-gp on the biophysical properties of lipid bilayers. Using a mixed detergent system it was possible to efficiently reconstitute P-gp at lipid:protein ratios as low as 2.

A bacterial antibiotic-resistance gene that complements the human multidrug-resistance P-glycoprotein gene.

Bacteria have developed many fascinating antibiotic-resistance mechanisms. A protein in Lactococcus lactis, LmrA, mediates antibiotic resistance by extruding amphiphilic compounds from the inner leaflet of the cytoplasmic membrane. Unlike other known bacterial multidrug-resistance proteins, LmrA is an ATP-binding cassette (ABC) transporter.

Transforming growth factor-beta is a renin secretagogue at picomolar concentrations.

Transforming growth factor-beta s (TGF-beta s), a family of peptides, have many actions including modulating cellular growth, differentiation, and influencing steroidogenesis. Because both TGF-beta and renin are present in renal juxtaglomerular cells, we have examined the effects of these peptides on renin secretion using static incubations of rat renal cortical slices. We report here an effect of both TGF-beta 1 and -beta 2 on renin secretion.