Mechanism and Role of Globin-Coupled Sensor Signalling

Abstract

The discovery of the globin-coupled sensor (GCS) family of haem proteins has provided new insights into signalling proteins and pathways by which organisms sense and respond to changing oxygen levels. GCS proteins consist of a sensor globin domain linked to a variety of output domains, suggesting roles in controlling numerous cellular pathways, and behaviours in response to changing oxygen concentration. Members of this family of proteins have been identified in the genomes of numerous organisms and characterization of GCS with output domains, including methyl accepting chemotaxis proteins, kinases, and diguanylate cyclases, have yielded an understanding of the mechanism by which oxygen controls activity of GCS protein output domains, as well as downstream proteins and pathways regulated by GCS signalling. Future studies will expand our understanding of these proteins both in vitro and in vivo, likely demonstrating broad roles for GCS in controlling oxygen-dependent microbial physiology and phenotypes.

π-Helix controls activity of oxygen-sensing diguanylate cyclases

“…Based on these studies a compact GCS structure, which depends on the middle domain π-helix for orienting the three domains, is needed for DGC activity and allows for direct sensor domain interactions with both middle and output domains to transmit the O 2 binding signal. The insights from the present study improve our understanding of DGC regulation and provide insight into GCS signaling that may lead to the ability to rationally control O 2 -dependent GCS activity.identified in numerous bacteria with a variety of output domains that are regulated by the O 2 -binding signal, including methyl accepting chemotaxis protein (MCP), kinase, and diguanylate cyclase (DGC) [12,13]. In Bacillus subtilis, the MCP-containing GCS regulates aerotaxis, allowing the organism to move to its preferred location within an O 2 gradient [14].…”

“…In Bacillus subtilis, the MCP-containing GCS regulates aerotaxis, allowing the organism to move to its preferred location within an O 2 gradient [14]. In contrast, the DGC-containing GCS from the plant pathogen Pectobacterium carotovorum (PccGCS) regulates O 2 -dependent motility, virulence factor production, and rotting within a plant host, highlighting the importance of O 2 sensing and GCS proteins in controlling bacterial phenotypes [11].Within the GCS protein family, the most common effect of O 2 binding to the heme of the globin domain is an increase in the activity of the output domain [13]. This increase in GCS enzymatic activity often requires oligomerization of GCS monomers to yield activity of the output domains; GCS proteins with diguanylate cyclase, histidine kinase, and adenylate cylcase output domains have been shown to function as homodimers and higher order oligomers [15][16][17][18][19][20].…”

“…identified in numerous bacteria with a variety of output domains that are regulated by the O 2 -binding signal, including methyl accepting chemotaxis protein (MCP), kinase, and diguanylate cyclase (DGC) [12,13]. In Bacillus subtilis, the MCP-containing GCS regulates aerotaxis, allowing the organism to move to its preferred location within an O 2 gradient [14].…”

“…Within the GCS protein family, the most common effect of O 2 binding to the heme of the globin domain is an increase in the activity of the output domain [13]. This increase in GCS enzymatic activity often requires oligomerization of GCS monomers to yield activity of the output domains; GCS proteins with diguanylate cyclase, histidine kinase, and adenylate cylcase output domains have been shown to function as homodimers and higher order oligomers [15][16][17][18][19][20].…”

In silico characterization of a novel putative aerotaxis chemosensory system in the myxobacterium, Corallococcus coralloides

“…MCP proteins with TM domains generally sense extracellular signals, whereas those lacking TM domains (cytoplasmic MCPs) sense intracellular signals such as those involved in energy taxis [ 12 , 25 , 26 ]. Diverse LBD domains involved in various energy taxis functions include PAS domains for sensing oxygen, redox potential, small ligands, and cumulatively energy levels of a cell [ 28 – 30 ], GAF domains for sensing light [ 31 ], and globin domains for direct oxygen sensing [ 32 ]. Among these, aerotaxis, whereby the cells move towards or away from oxygen in search of an optimal oxygen concentration for their metabolic state, is the most studied form of energy taxis.…”