basic helix-loop-helix-Per-ARNT-Sim (bHLH-PAS) domain found in Drosophila melanogaster Circadian locomotor output cycles protein kaput (dCLOCK) and similar proteins; dCLOCK, also termed dPAS1, is a bHLH-PAS Circadian regulator that acts as a transcription factor and generates a rhythmic output with a period of about 24 hours.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 62472090   11 TKSFLCRKSRNLSEKKRRDQFNSLVNDLSALISTSSRKMDKSTVLKSTIAFLKNHNEATDRSKVFEIQQDWKPAFL 86
Cdd:cd19735    5 EKDTIKRKSRNLSEKKRRDQFNVLINELCSMVSTSNRKMDKSTVLKSTIAFLKNHNEVTMQSHQQEIQEDWKPSFL 80

PAS domain; PAS motifs appear in archaea, eubacteria and eukarya. Probably the most surprising identification of a PAS domain was that in EAG-like K+-channels.

                            10        20        30        40        50        60
                    ....*....|....*....|....*....|....*....|....*....|....*....|.
gi 62472090      93 HLMLESLDGFMMVFSSMGSIFYASESITSQLGYLPQDLYNMTIYDLAYEMDHEALLNIFMN 153
Cdd:smart00091    4 RAILESLPDGIFVLDLDGRILYANPAAEELLGYSPEELIGKSLLELIHPEDRERVQEALQR 64

basic helix-loop-helix-Per-ARNT-Sim (bHLH-PAS) domain found in Drosophila melanogaster Circadian locomotor output cycles protein kaput (dCLOCK) and similar proteins; dCLOCK, also termed dPAS1, is a bHLH-PAS Circadian regulator that acts as a transcription factor and generates a rhythmic output with a period of about 24 hours.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 62472090   11 TKSFLCRKSRNLSEKKRRDQFNSLVNDLSALISTSSRKMDKSTVLKSTIAFLKNHNEATDRSKVFEIQQDWKPAFL 86
Cdd:cd19735    5 EKDTIKRKSRNLSEKKRRDQFNVLINELCSMVSTSNRKMDKSTVLKSTIAFLKNHNEVTMQSHQQEIQEDWKPSFL 80

PAS domain; PAS motifs appear in archaea, eubacteria and eukarya. Probably the most surprising identification of a PAS domain was that in EAG-like K+-channels. PAS domains have been found to bind ligands, and to act as sensors for light and oxygen in signal transduction.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 62472090  264 SNEFTSKHSMEWKFLFLDHRAPPIIGYMPFEVLGTSGYDYYHFDDLDSIVACHEELRQTGEGKSCYYRFLTKGQQWIWLQ 343
Cdd:cd00130    1 LPDGVIVLDLDGRILYANPAAEQLLGYSPEELIGKSLLDLIHPEDREELRERLENLLSGGEPVTLEVRLRRKDGSVIWVL 80

                         90       100
                 ....*....|....*....|...
gi 62472090  344 TDYYVSYHQFNSKPDYVVCTHKV 366
Cdd:cd00130   81 VSLTPIRDEGGEVIGLLGVVRDI 103

Helix-loop-helix DNA-binding domain;

                           10        20        30        40
                   ....*....|....*....|....*....|....*....|....*....
gi 62472090     17 RKSRNLSEKKRRDQFNSLVNDLSALI--STSSRKMDKSTVLKSTIAFLK 63
Cdd:pfam00010    2 REAHNERERRRRDRINDAFDELRELLptLPPDKKLSKAEILRLAIEYIK 50

PAS domain; PAS motifs appear in archaea, eubacteria and eukarya. Probably the most surprising identification of a PAS domain was that in EAG-like K+-channels.

                            10        20        30        40        50        60
                    ....*....|....*....|....*....|....*....|....*....|....*....|....
gi 62472090     258 SIIDpTSNEFTSKHSMEWKFLFLDHRAPPIIGYMPFEVLGTSGYDYYHFDDLDSIVACHEELRQ 321
Cdd:smart00091    5 AILE-SLPDGIFVLDLDGRILYANPAAEELLGYSPEELIGKSLLELIHPEDRERVQEALQRLLS 67

PAS fold; The PAS fold corresponds to the structural domain that has previously been defined as PAS and PAC motifs. The PAS fold appears in archaea, eubacteria and eukarya. This domain can bind gases (O2, CO and NO), FAD, 4-hydroxycinnamic acid and NAD+ (Matilla et.al., FEMS Microbiology Reviews, fuab043, 45, 2021, 1. https://doi.org/10.1093/femsre/fuab043).

                           10        20        30        40        50        60
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 62472090     95 MLESLDGFMMVFSSMGSIFYASESITSQLGYLPQDLYNMTIYDLAYEMDHEALLNIFMNPTPVIEPRQT 163
Cdd:pfam00989    6 ILESLPDGIFVVDEDGRILYVNAAAEELLGLSREEVIGKSLLDLIPEEDDAEVAELLRQALLQGEESRG 74

basic helix-loop-helix-Per-ARNT-Sim (bHLH-PAS) domain found in Drosophila melanogaster Circadian locomotor output cycles protein kaput (dCLOCK) and similar proteins; dCLOCK, also termed dPAS1, is a bHLH-PAS Circadian regulator that acts as a transcription factor and generates a rhythmic output with a period of about 24 hours.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 62472090   11 TKSFLCRKSRNLSEKKRRDQFNSLVNDLSALISTSSRKMDKSTVLKSTIAFLKNHNEATDRSKVFEIQQDWKPAFL 86
Cdd:cd19735    5 EKDTIKRKSRNLSEKKRRDQFNVLINELCSMVSTSNRKMDKSTVLKSTIAFLKNHNEVTMQSHQQEIQEDWKPSFL 80

basic helix-loop-helix-Per-ARNT-Sim (bHLH-PAS) domain found in neuronal PAS domain-containing protein 2 (NPAS2) and similar proteins; NPAS2, also termed neuronal PAS2, or basic-helix-loop-helix-PAS protein MOP4, or Class E basic helix-loop-helix protein 9 (bHLHe9), or member of PAS protein 4, or PAS domain-containing protein 4 (PASD4), is a bHLH-PAS transcriptional activator which forms a core component of the circadian clock.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 62472090   17 RKSRNLSEKKRRDQFNSLVNDLSALISTSSRKMDKSTVLKSTIAFLKNHNEATDRSKVFEIQQDWKP 83
Cdd:cd19737   11 RASRNKSEKKRRDQFNVLIKELSSMLPGNTRKMDKTTVLEKVIGFLQKHNEVSAQTEICDIQQDWKP 77

basic helix-loop-helix-Per-ARNT-Sim (bHLH-PAS) domain found in Circadian locomotor output cycles protein kaput (CLOCK) and similar proteins; CLOCK, also termed Class E basic helix-loop-helix protein 8 (bHLHe8), is a bHLH-PAS transcriptional activator which forms a core component of the circadian clock. It forms heterodimers with another bHLH-PAS protein, Brain-Muscle-Arnt-Like (also known as BMAL or ARNT3 or mop3), which regulates circadian rhythm. BMAL1-CLOCK heterodimer complex activates transcription from E-box (CANNTG) elements found in the promoter of circadian responsive genes.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|...
gi 62472090   17 RKSRNLSEKKRRDQFNSLVNDLSALISTSSRKMDKSTVLKSTIAFLKNHNEAT 69
Cdd:cd19734    8 RVSRNKSEKKRRDQFNVLIKELGSMLPGNARKMDKSTVLQKSIDFLRKHKEIT 60

basic helix-loop-helix-Per-ARNT-Sim (bHLH-PAS) domain found in circadian clock protein PASD1; PASD1, also termed PAS domain-containing protein 1, is evolutionarily related to Circadian locomotor output cycles protein kaput (CLOCK)and functions as a suppressor of the biological clock that drives the daily circadian rhythms of cells throughout the body. Mammalian PASD1 doesn't harbor the bHLH-PAS domain and is not included in this family.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|....*....
gi 62472090   17 RKSRNLSEKKRRDQFNSLVNDLSALISTSSR--KMDKSTVLKSTIAFLKNHNEATDRSK 73
Cdd:cd19736   11 RASRNKSEKKRRDQFNVLIKELCTMLQGHGHplKMDKSTILQRTIDFLQKQKEITAQTE 69

basic helix-loop-helix-Per-ARNT-Sim (bHLH-PAS) domain family; bHLH-PAS domain has been found in a large group of bHLH transcription regulators that are involved in gene expression responding to environmental change and controlling aspects of neural development, including proteins from aryl hydrocarbon receptor nuclear translocator (ARNT) family, hypoxia-inducible factor (HIF) family, aryl hydrocarbon receptor (AhR) family, neuronal PAS domain-containing protein (NPAS) family, Circadian locomotor output cycles protein kaput (CLOCK)-like family, and single-minded (SIM) family. bHLH-PAS transcriptional regulatory factors have a bHLH DNA-binding domain followed by two PAS domains and a C-terminal activation or repression domain. bHLH-PAS family members can be divided into class I and class II based on their dimerization partner. bHLH-PAS class I factors include AhR, HIF and SIM. The best characterized bHLH-PAS Class II protein is the ubiquitous ARNT. Some members of bHLH-PAS family act as transcriptional coactivators (such as NCoA) that lack the ability to dimerize and bind DNA.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|....*
gi 62472090   17 RKSRNLSEKKRRDQFNSLVNDLSAL---ISTSSRKMDKSTVLKSTIAFLKNHNEA 68
Cdd:cd11391    1 REKSREAAKKRRDKENAEISELASLlplPPAVGSKLDKLSVLRLAVAYLRLKKFL 55

basic helix-loop-helix-Per-ARNT-Sim (bHLH-PAS) domain found in aryl hydrocarbon receptor nuclear translocator-like protein 1 (ARNTL) and similar proteins; ARNTL, also termed Basic-helix-loop-helix-PAS protein MOP3, or brain and muscle ARNT-like 1 (BMAL1), or Class E basic helix-loop-helix protein 5 (bHLHe5), or member of PAS protein 3, or PAS domain-containing protein 3 (PASD3), or bHLH-PAS protein JAP3, is a member of the bHLH-PAS transcription factor family that forms heterodimers with another bHLH-PAS protein, CLOCK (circadian locomotor output cycle kaput), which regulates circadian rhythm. ARNTL-CLOCK heterodimer complex activates transcription from E-box (CANNTG) elements found in the promoter of circadian responsive genes. ARNTL is highly homologous to ARNT.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|....*..
gi 62472090   17 RKSRNLSEKKRRDQFNSLVNDLSALISTS---SRKMDKSTVLKSTIAFLKNHNEATD 70
Cdd:cd11438    8 REAHSQIEKRRRDKMNSFIDELASLVPTCnamSRKLDKLTVLRMAVQHMKTLRGATN 64

basic helix-loop-helix-Per-ARNT-Sim (bHLH-PAS) domain found in Drosophila melanogaster protein cycle and similar proteins; Protein cycle, also termed brain and muscle ARNT-like 1 (BMAL1), or MOP3, is a putative bHLH-PAS transcription factor involved in the generation of biological rhythms in Drosophila. It activates cycling transcription of Period (PER) and Timeless (TIM) by binding to the E-box (5'-CACGTG-3') present in their promoters.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|...
gi 62472090   24 EKKRRDQFNSLVNDLSALI---STSSRKMDKSTVLKSTIAFLK 63
Cdd:cd19726    9 EKRRRDKMNTYITELSSMIpmcNAMSRKLDKLTVLRMAVQHMK 51

Helix-loop-helix DNA-binding domain;

                           10        20        30        40
                   ....*....|....*....|....*....|....*....|....*....
gi 62472090     17 RKSRNLSEKKRRDQFNSLVNDLSALI--STSSRKMDKSTVLKSTIAFLK 63
Cdd:pfam00010    2 REAHNERERRRRDRINDAFDELRELLptLPPDKKLSKAEILRLAIEYIK 50

basic helix-loop-helix-orange (bHLH-O) domain found in hairy and enhancer of split (HES)-related repressor protein (HERP)-like family; The HERP-like family includes bHLH-O transcriptional regulators that are related to the Drosophila hairy and Enhancer-of-split proteins. They contain a basic helix-loop-helix (bHLH) domain with an invariant glycine residue in its basic region, an orange domain in the central region and YXXW sequence motif at its C-terminal region. HERP proteins (HEY1, HEY2 and HEYL) act as downstream effectors of Notch signaling. They are involved in cardiovascular development and have roles in somitogenesis, myogenesis and gliogenesis. Hairy and enhancer of split-related protein HELT is a transcriptional repressor expressed in the developing central nervous system. It binds preferentially to the canonical E box sequence 5'-CACGCG-3' and regulates neuronal differentiation and/or identity. Differentially expressed in chondrocytes proteins, DEC1 and DEC2, are widely expressed in both embryonic and adult tissues and have been implicated in apoptosis, cell proliferation, and circadian rhythms, as well as malignancy in various cancers. Drosophila melanogaster protein clockwork orange (Cwo) is also included in this family. It is involved in the regulation of Drosophila circadian rhythms. It functions as both an activator and a repressor of clock gene expression.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|....*
gi 62472090   24 EKKRRDQFNSLVNDLSALI-----STSSRKMDKSTVLKSTIAFLK 63
Cdd:cd11389    5 EKRRRDRINESLAELRRLVpearkSKGSGKLEKAEILEMTLQHLK 49

basic Helix-Loop-Helix-zipper (bHLHzip) domain found in transcription factor E3 (TFE3) and similar proteins; TFE3, also termed Class E basic helix-loop-helix protein 33 (bHLHe33), is a bHLHzip transcription factor that is involved in B cell function. It specifically recognizes and binds E-box sequences (5'-CANNTG-3'). Its efficient DNA-binding requires dimerization with itself or with another MiT/TFE family member such as TFEB or MITF.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 62472090   17 RKSRNLSEKKRRDQFNSLVNDLSALISTSS---RKMDKSTVLKSTIAFLKNHNEATDRSKVFEIQQ 79
Cdd:cd18928   12 KDNHNLIERRRRFNINDRIKELGTLIPKSTdpeMRWNKGTILKASVDYIRKLQKEQQRSKEIEMRQ 77

basic helix-loop-helix-orange (bHLH-O) domain found in hairy/enhancer-of-split related with YRPW motif-like protein (HEYL) and similar proteins; HEYL, also termed Class B basic helix-loop-helix protein 33 (bHLHb33), or hairy-related transcription factor 3 (HRT-3), is a bHLH-O transcriptional repressor that is strongly expressed in the presomitic mesoderm, the somites, the peripheral nervous system and smooth muscle of all arteries and is a downstream effector of the Notch and transforming growth factor-beta pathways. It promotes neuronal differentiation by activating proneural genes and inhibiting other hairy and enhancer of split (HES) and hairy/enhancer-of-split related with YRPW motif protein (HEY) proteins. HEYL also functions as a tumor suppressor involved in the progression of human cancers.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|..
gi 62472090   17 RKSRNLSEKKRRDQFNSLVNDLSALISTS-----SRKMDKSTVLKSTIAFLK 63
Cdd:cd11447   10 KKRRGIIEKRRRDRINSSLSELRRLVPTAfekqgSSKLEKAEILQMTVDHLK 61

basic helix-loop-helix-orange (bHLH-O) domain found in hairy and enhancer of split (HES)-related repressor protein (HERP) family; HERP (also called Hey/Hesr/HRT/CHF/gridlock) proteins corresponds to a family of bHLH-O transcriptional repressors that are related to the Drosophila hairy and Enhancer-of-split proteins and act as downstream effectors of Notch signaling. They contain a basic helix-loop-helix (bHLH) domain with an invariant glycine residue in its basic region, an orange domain in the central region and YXXW sequence motif at its C-terminal region. HERP proteins are involved in cardiovascular development and have roles in somitogenesis, myogenesis and gliogenesis.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|...
gi 62472090   17 RKSRNLSEKKRRDQFNSLVNDLSALIST-----SSRKMDKSTVLKSTIAFLKN 64
Cdd:cd11407    2 KKRRGIIEKRRRDRINNSLAELRRLVPTafekqGSAKLEKAEILQMTVDHLKM 54

basic helix-loop-helix (bHLH) domain found in Arabidopsis thaliana protein IAA-leucine resistant 3 (ILR3) and similar proteins; ILR3, also termed AtbHLH105, or EN 133, is a bHLH transcription factor that plays a role in resistance to amide-linked indole-3-acetic acid (IAA) conjugates such as IAA-Leu and IAA-Phe. It may regulate gene expression in response to metal homeostasis changes.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|.
gi 62472090   24 EKKRRDQFNSLVNDLSALIS-TSSRKMDKSTVLKSTIAFLK 63
Cdd:cd11446    5 EKLRRDKLNERFMELSNVLEpGRPPKTDKATILGDAIRMLK 45

basic Helix-Loop-Helix-zipper (bHLHzip) domain found in Max-like protein X (Mlx) family; Mlx, also termed Class D basic helix-loop-helix protein 13 (bHLHd13), or Max-like bHLHZip protein, or protein BigMax, or transcription factor-like protein 4, is a Max-like bHLHZip transcription regulator that interacts with the Max network of transcription factors. It forms a sequence-specific DNA-binding protein complex with some member of Mad family (Mad1 and Mad4) and Mondo family but not the Myc family and bind the E-box DNA to control transcription. The family also includes Saccharomyces cerevisiae INO4, which is a bHLH transcriptional activator of phospholipid synthetic genes (such as INO1, CHO1/PSS, CHO2/PEM1, OPI3/PEM2, etc.). It is required for de-repression of phospholipid biosynthetic gene expression in response to inositol deprivation in yeast.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|....*...
gi 62472090   17 RKSRNLSEKKRRDQFNSLVNDLSALI-STSSRKMDKSTVLKSTIAFLK 63
Cdd:cd11404    3 RLNHVRSEKKRRELIKKGYDELCALVpGLDPQKRTKADILQKAADWIQ 50

basic helix-loop-helix-Per-ARNT-Sim (bHLH-PAS) domain found in steroid receptor coactivator (SRC) family; The SRC family of coactivators includes SRC-1 (NcoA-1/p160), SRC-2(TIF2/GRIP1/NcoA-2) and SRC-3(NcoA-3/pCIP/RAC3/ACTR/pCIP/AIB1/TRAM1), which are critical mediators of steroid receptor action. They contain bHLH-PAS domain at the N-terminal that is followed by receptor interacting domain and C-terminal transcriptional activation domain. SRC coactivators interact with nuclear receptors in a ligand-dependent manner and enhance transcriptional activation by the receptor via histone acetylation/methylation.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|....*...
gi 62472090   19 SRNLSEKKRRDQFNSLVNDLSALISTS-------SRKMDKSTVLKSTI 59
Cdd:cd11439    1 NKCLNEKRRREQENKYIEELAELISASisdmdslSVKPDKCAILQETV 48

PAS fold; The PAS fold corresponds to the structural domain that has previously been defined as PAS and PAC motifs. The PAS fold appears in archaea, eubacteria and eukarya. This domain can bind gases (O2, CO and NO), FAD, 4-hydroxycinnamic acid and NAD+ (Matilla et.al., FEMS Microbiology Reviews, fuab043, 45, 2021, 1. https://doi.org/10.1093/femsre/fuab043).

                           10        20        30        40        50        60
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 62472090     95 MLESLDGFMMVFSSMGSIFYASESITSQLGYLPQDLYNMTIYDLAYEMDHEALLNIFMNPTPVIEPRQT 163
Cdd:pfam00989    6 ILESLPDGIFVVDEDGRILYVNAAAEELLGLSREEVIGKSLLDLIPEEDDAEVAELLRQALLQGEESRG 74

basic helix-loop-helix-Per-ARNT-Sim (bHLH-PAS) domain found in aryl hydrocarbon receptor nuclear translocator (ARNT) and similar proteins; ARNT, also termed Class E basic helix-loop-helix protein 2 (bHLHe2), or Dioxin receptor, nuclear translocator, or hypoxia-inducible factor 1-beta (HIF1b), or HIF-1-beta, or HIF1-beta, is a member of bHLH-PAS transcription regulators that acts as the heterodimeric partner for bHLH-PAS proteins such as aryl hydrocarbon receptor (AhR), hypoxia-inducible factor (HIF), and single-minded (SIM). These bHLH-PAS transcription complexes are involved in transcriptional responses to xenobiotic, hypoxia, and developmental pathways. Heterodimerization of bHLH-PAS proteins with ARNT is mediated by contacts between both the bHLH and the tandem PAS domains. ARNT use bHLH and/or PAS domains to interact with several transcriptional coactivators. It is required for activity of the aryl hydrocarbon (dioxin) receptor.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|....*
gi 62472090   12 KSFLCRKSRNLSEKKRRDQFNSLVNDLSALISTSS---RKMDKSTVLKSTIAFLK 63
Cdd:cd18947    1 KERFARENHSEIERRRRNKMTAYITELSDMVPTCSalaRKPDKLTILRMAVSHMK 55

basic helix-loop-helix-orange (bHLH-O) domain found in hairy/enhancer-of-split related with YRPW motif protein 1 (HEY1) and similar proteins; HEY1, also termed cardiovascular helix-loop-helix factor 2 (CHF-2), or Class B basic helix-loop-helix protein 31 (bHLHb31), or HES-related repressor protein 1, or hairy and enhancer of split-related protein 1 (HESR-1), or hairy-related transcription factor 1 (HRT-1), is a bHLH-O transcriptional repressor that acts as an essential downstream effector of the Notch signaling pathway and may play a fundamental role in vascular development. HEY1 also participates several cancer-related pathways. It acts as a positive regulator of the tumor suppressor p53.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|..
gi 62472090   17 RKSRNLSEKKRRDQFNSLVNDLSALISTS-----SRKMDKSTVLKSTIAFLK 63
Cdd:cd19748   10 KRRRGIIEKRRRDRINNSLSELRRLVPSAfekqgSAKLEKAEILQMTVDHLK 61

basic helix-loop-helix-orange (bHLH-O) domain found in hairy and enhancer of split (HES) family; The HES family includes bHLH-O transcriptional regulators that are related to the Drosophila hairy and Enhancer-of-split (HES) proteins. They contain a basic helix-loop-helix (bHLH) domain with an invariant proline residue in its basic region, an orange domain in the central region and a conserved tetrapeptide motif, WRPW, at its C-terminal region. HES family proteins form heterodimers or homodimers via their HLH domain and bind DNA to repress gene transcription that play an essential role in development of both compartment and boundary cells of the central nervous system.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|
gi 62472090   24 EKKRRDQFNSLVNDLSALI-------STSSRKMDKSTVLKSTIAFLKNHN 66
Cdd:cd11410    2 EKKRRARINKSLEQLKTLVlealnkdNTRYSKLEKADILEMTVKYLKQLQ 51

basic Helix-Loop-Helix-zipper (bHLHzip) domain found in sterol regulatory element-binding protein (SREBP) family; The SREBP family includes SREBP1 and SREBP2, which are bHLHzip transcriptional activator of genes encoding proteins essential for cholesterol biosynthesis/uptake and fatty acid biosynthesis. SREBP1 and SREBP2 are principally found in the liver and in adipocytes and made up of an N-terminal transcription factor portion (composed of an activation domain, a bHLHzip domain, and a nuclear localization signal), a hydrophobic region containing two membrane spanning regions, and a C-terminal regulatory segment. They recognize a symmetric sterol regulatory element (TCACNCCAC) instead of E-box.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|....*...
gi 62472090   17 RKSRNLSEKKRRDQFNSLVNDLSALISTSSRKMDKSTVLKSTIAFLKN 64
Cdd:cd11394    7 RSAHNAIEKRYRSSINDRIIELKDLVVGPDAKMNKSAVLRKAIDYIRY 54

basic helix-loop-helix (bHLH) domain found in Arabidopsis thaliana protein NAI1 and similar proteins; NAI1, also termed AtbHLH20, or EN 27, is a bHLH transcription activator that regulates the expression of at least NAI2, PYK10 and PBP1. It is required for and mediates the formation of endoplasmic reticulum bodies (ER bodies). It plays a role in the symbiotic interactions with the endophytes of the Sebacinaceae fungus family, such as Piriformospora indica and Sebacina.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|....*..
gi 62472090   22 LSEKKRRDQFNSLVNDLSALIStSSRKMDKSTVLKSTIAFLKNHNEatdRSKVFEIQ 78
Cdd:cd11452    8 LAERKRREKLSQRFIALSALVP-GLKKMDKASVLGDAIKHIKQLQE---RVKELEEE 60