Streptavidin cooperative allosterism upon binding biotin observed by differential changes in intrinsic fluorescence.

While the binding of biotin by streptavidin does not appear to be cooperative in the traditional sense of altered binding strength, it has been suggested that it may be cooperative in terms of differential structural changes in the protein. In this work we present intrinsic tryptophan fluorescence data as evidence of a cooperative structural change. The technique involves examination of the differences in fluorescence emission corresponding to distinct tryptophan populations accompanying protein-ligand binding.

IL-27 and type 2 immunity in asthmatic patients: association with severity, CXCL9, and signal transducer and activator of transcription signaling.

Background: Severe asthma (SA) can involve both innate and type 2 cytokine-associated adaptive immunity. Although IL-27 has been reported to potentiate TH1 responses (including the chemokine CXCL9) and suppress TH2 responses, its function in asthmatic patients is unknown.

Objective: We sought to evaluate IL-27 expression in human asthma alone and in combination with type 2 immunity to determine the relationship to disease severity and CXCL9 expression.

A connecting hinge represses the activity of endothelial nitric oxide synthase.

In mammals, endothelial nitric oxide synthase (eNOS) has the weakest activity, being one-tenth and one-sixth as active as the inducible NOS (iNOS) and the neuronal NOS (nNOS), respectively. The basis for this weak activity is unclear. We hypothesized that a hinge element that connects the FMN module in the reductase domain but is shorter and of unique composition in eNOS may be involved.