The role of intersubunit interactions for the stabilization of the T state of Escherichia coli aspartate transcarbamoylase.

Homotropic cooperativity in Escherichia coli aspartate transcarbamoylase results from the substrate-induced transition from the T to the R state. These two alternate states are stabilized by a series of interdomain and intersubunit interactions. The salt link between Lys-143 of the regulatory chain and Asp-236 of the catalytic chain is only observed in the T state.

Cytokines induce indoleamine 2,3-dioxygenase expression in human atheroma-asociated cells: implications for persistent Chlamydophila pneumoniae infection.

This study shows that vascular smooth muscle cells express significantly higher levels of gamma interferon-inducible indoleamine 2,3-dioxygenase (IDO) activity than endothelium or mononuclear cells. Since IDO activity is linked to persistent Chlamydophila pneumoniae infection, our results suggest that smooth muscle cells may be an important reservoir of that organism in atherosclerosis.