PlantTFDB
Plant Transcription Factor Database
v4.0
Previous version: v1.0, v2.0, v3.0
Lactuca sativa
bHLH Family
Species TF ID Description
Lsa000009bHLH family protein
Lsa000147bHLH family protein
Lsa000323bHLH family protein
Lsa000661bHLH family protein
Lsa001101bHLH family protein
Lsa001529bHLH family protein
Lsa001604bHLH family protein
Lsa001938bHLH family protein
Lsa002174bHLH family protein
Lsa002459bHLH family protein
Lsa003280bHLH family protein
Lsa003371bHLH family protein
Lsa003559bHLH family protein
Lsa003599bHLH family protein
Lsa003891bHLH family protein
Lsa004050bHLH family protein
Lsa004104bHLH family protein
Lsa004150bHLH family protein
Lsa004584bHLH family protein
Lsa005032bHLH family protein
Lsa005237bHLH family protein
Lsa005287bHLH family protein
Lsa005293bHLH family protein
Lsa005496bHLH family protein
Lsa006550bHLH family protein
Lsa006633bHLH family protein
Lsa006688bHLH family protein
Lsa006953bHLH family protein
Lsa007194bHLH family protein
Lsa007224bHLH family protein
Lsa007390bHLH family protein
Lsa007709bHLH family protein
Lsa007987bHLH family protein
Lsa008285bHLH family protein
Lsa008457bHLH family protein
Lsa008880bHLH family protein
Lsa009233bHLH family protein
Lsa009691bHLH family protein
Lsa009711bHLH family protein
Lsa009814bHLH family protein
Lsa009820bHLH family protein
Lsa010988bHLH family protein
Lsa011015bHLH family protein
Lsa011180bHLH family protein
Lsa011189bHLH family protein
Lsa011393bHLH family protein
Lsa011783bHLH family protein
Lsa011853bHLH family protein
Lsa012219bHLH family protein
Lsa012414bHLH family protein
Lsa012624bHLH family protein
Lsa012711bHLH family protein
Lsa012854bHLH family protein
Lsa012872bHLH family protein
Lsa013005bHLH family protein
Lsa013456bHLH family protein
Lsa013616bHLH family protein
Lsa013641bHLH family protein
Lsa013647bHLH family protein
Lsa013654bHLH family protein
Lsa013731bHLH family protein
Lsa014695bHLH family protein
Lsa015345bHLH family protein
Lsa015449bHLH family protein
Lsa015598bHLH family protein
Lsa015840bHLH family protein
Lsa016155bHLH family protein
Lsa016348bHLH family protein
Lsa016738bHLH family protein
Lsa017573bHLH family protein
Lsa017580bHLH family protein
Lsa017876bHLH family protein
Lsa017982bHLH family protein
Lsa018657bHLH family protein
Lsa018858bHLH family protein
Lsa019025bHLH family protein
Lsa019076bHLH family protein
Lsa019205bHLH family protein
Lsa019461bHLH family protein
Lsa000472bHLH family protein
Lsa001431bHLH family protein
Lsa002867bHLH family protein
Lsa003534bHLH family protein
Lsa005813bHLH family protein
Lsa008340bHLH family protein
Lsa010140bHLH family protein
Lsa011221bHLH family protein
Lsa013922bHLH family protein
Lsa016168bHLH family protein
Lsa019015bHLH family protein
bHLH Family Introduction

The basic/helix-loop-helix (bHLH) proteins are a superfamily of transcription factors that have been well characterized in nonplant eukaryotes, especially in mammalian systems, in which considerable structural, functional, and phylogenetic analyses have been performed. The data indicate that bHLH proteins are important regulatory components in transcriptional networks in these systems, controlling a diversity of processes from cell proliferation to cell lineage establishment.

This family is defined by the bHLH signature domain, which consists of 60 amino acids with two functionally distinct regions. The basic region, located at the N-terminal end of the domain, is involved in DNA binding and consists of 15 amino acids with a high number of basic residues. The HLH region, at the C-terminal end, functions as a dimerization domain and is constituted mainly of hydrophobic residues that form two amphipathic -helices separated by a loop region of variable sequence and length. Outside of the conserved bHLH domain, these proteins exhibit considerable sequence divergence. Cocrystal structural analysis has shown that the interaction between the HLH regions of two separate polypeptides leads to the formation of homodimers and/or heterodimers and that the basic region of each partner binds to half of the DNA recognition sequence. Some bHLH proteins form homodimers or restrict their heterodimerization activity to closely related members of the family. On the other hand, some can form heterodimers with one or several different partners.

The core DNA sequence motif recognized by the bHLH proteins is a consensus hexanucleotide sequence known as the E-box (5'-CANNTG-3'). There are different types of E-boxes, depending on the identity of the two central bases. One of the most common is the palindromic G-box (5'-CACGTG-3'). Certain conserved amino acids within the basic region of the protein provide recognition of the core consensus site, whereas other residues in the domain dictate specificity for a given type of E-box . In addition, flanking nucleotides outside of the hexanucleotide core have been shown to play a role in binding specificity, and there is evidence that a loop residue in the protein plays a role in DNA binding through elements that lie outside of the core recognition sequence.

Toledo-Ortiz G, Huq E, Quail PH.
The Arabidopsis basic/helix-loop-helix transcription factor family.
Plant Cell. 2003 Aug;15(8):1749-70
PMID: 12897250