Development of a label-free assay for sodium-dependent phosphate transporter NaPi-IIb.

The most widely used assay format for characterizing plasma membrane transporter activity measures accumulation of radiolabeled substrates in tissues or cells expressing the transporters. This assay format had limitations and disadvantages; therefore, there was an unmet need for development of a homogeneous, nonradioactive assay for membrane transporter proteins. In this report, the authors describe the development of a label-free homogeneous assay for the sodium-dependent phosphate transporter NaPi-IIb using the Epic system.

Strategy for the identification of GPR23/LPA4 receptor agonists and inverse agonists.

Lysophosphatidic acid (LPA) is a bioactive phospholipid that signals through G-protein-coupled receptors to produce a range of biological responses. A recently reported LPA receptor GPR23 (LPA4 receptor) has a low homology to the LPA(1-3) receptors identified previously. In Chinese hamster ovary cells expressing the human GPR23, LPA induced an increase in cellular cyclic adenosine monophosphate (cAMP) and calcium levels.

A mutation in the folA promoter delays adaptation to minimal medium by Escherichia coli K-12.

In its natural environment, Escherichia coli is subjected to frequent changes in nutrients and physical parameters such as temperature. Adapting to new conditions requires an orderly progression of events. We show that a folA mutant that overexpressed dihydrofolate reductase because of a C to T promoter mutation, adapted very slowly when transferred from rich medium at 37 degrees C to glucose minimal medium at 42 degrees C.