Table 1

Classification of CNB domains in the public and GOS data

No.
Family name
NR/GOS count
Taxonomic origin
PBC consensus motif
Description

1
PKA-Rsub
301/0
Eukaryote
GELALIYGTPRAATVVA
cAMP dependent regulatory subunit that activates PKA
2
PKG
388/9
Eukaryote
GELALLYNDPRTATVIA
cGMP activated proteins that are typically attached to a kinase domain
3
PKG-parasites
362/11
Eukaryote
GERALLYDEPRSATIKA
A distinct group of PKGs in parasites that are also attached to kinase domains
4
Other_eukaryotic
940/201
Eukaryote
GELALLYNAPRAATVVA
CNB domains from metazoans and plants. These are attached to various functional domains such as PKs, PAS domains, PP2C like phosphatases and phospholipases
5
Epac
150/1
Eukaryote
GQLALVNDAPRAATIVL
cAMP-dependent guanine nucleotide exchange factors. Typically attached to an amino-terminal DEP domain and a carboxy-terminal RasGEF domain
6
PDZ-GEF
125/0
Eukaryote
GVSPTMDKEYMKGVMRT
A distinct class of Epac's, also called Epac6, which contains a PDZ domain in between the CNB and RasGEF domain. Epac's of this class contain a non-canonical PBC
7
K-channel
86/0
Eukaryote
GEVGVLCYRPQLFTVRT
Potassium channels specific to plants. Most of them contain an Ankryin repeat carboxy-terminal to the CNB domain
8
LR_CC
148/4
Eukaryote
GEIGVLLDPPRTATVRA
CNB domains found in metazoans and fungi, usually occur in tandem like the PKA regulatory subunit and contain a carboxy-terminal F-box domain and leucine rich domain
9
HCN
165/5
Eukaryote
GEICLLTRGRRTASVRA
cGMP-gated cation channels. Mostly present in metazoans
10
K_HCN
185/0
Eukaryote
GENFWLYGTKSNADVRA
Potassium channels that contain a PAC motif (motif carboxy-terminal of PAS) amino-terminal of the trans-membrane segment. This subfamily also contains a non-canonical PBC
11
Channel_Tetrahym.
218/44
Eukaryote
GEEDFFSGQPRTFTAKC
Likely HCN channels from the single celled eukaryote Tetrahymena thermophila. This subfamily is quite distinct from the HCN channels in higher eukaryotes
12
Channel_protozoa
587/41
Eukaryote
GEISFFTGLPRTASARS
Other HCN channels in protozoans
13
Bact_Pyrredox
38/70
Prokaryote
GEMGLISGRRRGATVRA
Tandem CNB domains that are attached to an amino-terminal pyridine nucleotide-disulphide oxidoreductase domain
14
Channel_Bact
99/79
Prokaryote
GEIALLTGGPRTATVRA
Bacterial CNBs that are attached to mechanosensitive ion channels
15
HisK
56/11
Prokaryote
GELSLLTGGPRSATVRA
Bacterial CNBs that contain a HisK like ATPase, carboxy-terminal of the CNB domain
16
AAA_Atpase
65/24
Prokaryote
GEMALLSGQERKASVIA
A distinct sub-group containing AAA-ATPase domains attached to the CNB domain. Several members of this group contain an ABC-transporter like transmembrane region. The PBC arginine (Arg209) is quite variable within this family
17
NtcA
108/104
Prokaryote
GVLSLLTGSDRFYHAVA
Nitrogen responsive regulatory protein that contains a DNA binding domain (HTH) carboxy-terminal of the CNB domain
18
FixK
43/0
Prokaryote
G-ASLGGDHLFTAEA
Involved in nitrogen fixation and contains a HTH motif
19
FnR
176/53
Prokaryote
GEFDAIGSGHHPSFAQA
Transcriptional regulators that are implicated in oxygen sensing
20
ArcR
29/0
Prokaryote
PYGGLFTDDYYHESATA
Transcriptional regulator that is implicated in the aerobic arginase reaction. Arginine is used as a source of energy in bacteria
21
NnR
28/0
Prokaryote
GFARALQRGDYPGTATA
Transcriptional regulators that act on the nir and nor operons to achieve expression under aerobic conditions
22
CBS
173/51
Prokaryote
GERALLAGGPYSLTARA
This group contains tandem CBS domain located carboxy-terminal of the CNB domain
23
Other_bacterial
1553/1486
Prokaryote
GEMALLDGEPRSATVVA
Bacterial CNB domains that are attached to various functional domains such as CheY response regulators, Rhodanese homology domain, kinases and DNA binding domains
24
HTH_ICLR
33/14
Prokaryote
GEGAAFSEEPRSTTVVA
Transcriptional regulator that is implicated in the repression of the acetate operon (also known as glyoxylate bypass operon) in Escherichia coli and Salmonella typhimurium
25
HTH_GNTR
85/52
Prokaryote
GEASLFDGEPRSATVVA
Transcriptional regulator containing a HTH domain and implicated in the repression of the gluconate operon
26
Flp
19/0
Prokaryote
GEEALFGESNHANYCEA
Involved in the bacterial oxidative stress response
27
HTH_ARSR
66/15
Prokaryote
GEAALFSNGPYPATAIA
Functions as a transcriptional repressor of an arsenic resistance operon. Dissociates from DNA in the presence of the metal
28
HTH_CRP
858/347
Prokaryote
GEAALFDGGPRPATAVA
Transcriptional regulation of the crp operon
29
HTH_MARR
143/20
Prokaryote
GEMALLDGGPRSADAVA
Repressor of genes that activate the multiple antibiotic resistance and oxidative stress regulons
30
HTH_ASNC
73/24
Prokaryote
GEIALLDGGPRSATATA
An autogenously regulated activator of asparagine synthetase A transcription in Escherichia coli

Kannan et al. Genome Biology 2007 8:R264   doi:10.1186/gb-2007-8-12-r264