TABLE 2

Characteristics of well-studied cytoplasmic chemoreceptorsa

Cytoplasmic receptorSpeciesDomain(s)Input or phenotypeLocalization(s)MethylationNo. of chemosensory systems (source or database[s])Reference(s)
NH3COOHConsensusVerified
TlpD (HP0599)H. pyloriNoneCZBElectron transport chain blockageP/CNoNo111, 49
Tm14 (TM0014)T. maritimaNoneNoneUnknownNDNDNo1 (Mist and MicrobesOnline)26, 42
McpS (PA1930)P. aeruginosaPAS (2)NoneOverexpression disrupts polar localization of transmembrane chemoreceptorsPYesND4 (Porter et al.)34
IcpA/McpE (SMc03004)S. melilotiProtoglobinNoneUnknownPNoNo2 (Porter et al.)61, 90
McpY (SMc03087)S. melilotiHAMP, PASNoneUnknownPYesND2 (Porter et al.)61, 90
HemAT (BSU10380)B. subtilisProtoglobinNoneProtoglobin-bound heme senses oxygenPYesYes1 (Porter et al.)14, 64
YfmS (BSU07360)B. subtilisNoneNoneUnknownPNDND1 (Porter et al.)14
AerC (AZOBR_70123)A. brasilensePAS (2)NoneCytoplasmic redox/oxygen via FAD bound in PAS domainP/CNDND4 (Russell et al.)12
TlpC (RSP_1589)R. sphaeroidesNoneNoneUnknownCCNo3 (Porter et al.)44, 91
TlpT (RSP_0044)R. sphaeroidesNoneNoneUnknownCCNo3 (Porter et al.)36, 67
FrzCD (MXAN_4141)M. xanthusNoneNoneSenses side-to-side contact from neighboring cells; fruiting body formationD, FYesYes8 (Porter et al.)74, 92, 93
Mcp7 (MXAN_6962)M. xanthusNoneNoneCoupling between sporulation and aggregationP (sub)NDND8 (Porter et al.)75
McpB (CC_0428)C. crescentusProtoglobinNoneUnknownCYesND2 (Mist, MicrobesOnline)35
Car (OE_5243F)H. salinarumPASNoneArginineCNDND1 (Mist)15
  • a Domains are given as either amino terminal (NH3) or carboxy terminal (COOH) relative to the MA domain. Localization is indicated as follows: P, polar; P/C, polar and cytoplasmic; P (sub), subpolar; CC, cytoplasmic clusters; D, cytoplasmic and dynamic; F, filaments; C, cytoplasmic but exact location unknown; ND, not determined. “Methylation consensus” indicates whether methylation consensus sequences have been identified in the protein, while “verified” indicates whether these were experimentally confirmed (Yes) or not yet determined (ND). Numbers of chemotaxis operons and encoded CheA proteins were obtained from data reported previously by Porter et al. (32) and Russell et al. (59) and in the Mist (94) and MicrobesOnline (95) databases, as indicated. This number is usually estimated based on the number of encoded CheA proteins.