Signal transduction histidine kinase, osmosensitive K+ channel sensor, N-terminal (IPR003852)

Short name: Sig_transdc_His_kinase_KdpD_N

Overlapping homologous superfamilies


Domain relationships



Signal transducing histidine kinases are the key elements in two-component signal transduction systems, which control complex processes such as the initiation of development in microorganisms [PMID: 8868347, PMID: 11406410]. Examples of histidine kinases are EnvZ, which plays a central role in osmoregulation [PMID: 10426948], and CheA, which plays a central role in the chemotaxis system [PMID: 9989504]. Histidine kinases usually have an N-terminal ligand-binding domain and a C-terminal kinase domain, but other domains may also be present. The kinase domain is responsible for the autophosphorylation of the histidine with ATP, the phosphotransfer from the kinase to an aspartate of the response regulator, and (with bifunctional enzymes) the phosphotransfer from aspartyl phosphate back to ADP or to water [PMID: 11145881]. The kinase core has a unique fold, distinct from that of the Ser/Thr/Tyr kinase superfamily.

HKs can be roughly divided into two classes: orthodox and hybrid kinases [PMID: 8029829, PMID: 1482126]. Most orthodox HKs, typified by the Escherichia coli EnvZ protein, function as periplasmic membrane receptors and have a signal peptide and transmembrane segment(s) that separate the protein into a periplasmic N-terminal sensing domain and a highly conserved cytoplasmic C-terminal kinase core. Members of this family, however, have an integral membrane sensor domain. Not all orthodox kinases are membrane bound, e.g., the nitrogen regulatory kinase NtrB (GlnL) is a soluble cytoplasmic HK [PMID: 10966457]. Hybrid kinases contain multiple phosphodonor and phosphoacceptor sites and use multi-step phospho-relay schemes instead of promoting a single phosphoryl transfer. In addition to the sensor domain and kinase core, they contain a CheY-like receiver domain and a His-containing phosphotransfer (HPt) domain.

This entry represents the N-terminal domain found in KdpD sensor kinase proteins, which regulate the kdpFABC operon responsible for potassium transport [PMID: 9226259]. The N-terminal domain forms part of the cytoplasmic region of the protein, which may be the sensor domain responsible for sensing turgor pressure [PMID: 1532388].

GO terms

Biological Process

GO:0000160 phosphorelay signal transduction system

Molecular Function

GO:0000155 phosphorelay sensor kinase activity
GO:0004673 protein histidine kinase activity

Cellular Component

GO:0016020 membrane

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.