The Dos family of globin-related sensors using PAS domains to accommodate haem acting as the active site for sensing external signals

Abstract

Sensor proteins play crucial roles in maintaining homeostasis of cells by sensing changes in extra- and intracellular chemical and physical conditions to trigger biological responses. It has recently become clear that gas molecules function as signalling molecules in these biological regulatory systems responsible for transcription, chemotaxis, synthesis/hydrolysis of nucleotide second messengers, and other complex physiological processes. Haem-containing sensor proteins are widely used to sense gas molecules because haem can bind gas molecules reversibly. Ligand binding to the haem in the sensor proteins triggers conformational changes around the haem, which results in their functional regulation. Spectroscopic and crystallographic studies are essential to understand how these sensor proteins function in these biological regulatory systems. In this chapter, I discuss structural and functional relationships of haem-containing PAS and PAS-related families of the sensor proteins.

Keywords: Aerotaxis; Chemotaxis; Diguanylate cyclase; EcDos; FixL; Haem-based sensor; PAS domain; Phosphodiesterase; Two-component system.