The AP2/ERF superfamily is defined by the AP2/ERF domain, which consists of about 60 to 70 amino acids and is involved in DNA binding. These three families have been defined as follows. The AP2 family proteins contain two repeated AP2/ERF domains, the ERF family proteins contain a single AP2/ERF domain, and the RAV family proteins contain a B3 domain, which is a DNA-binding domain conserved in other plant-specific transcription factors, in addition to the single AP2/ERF domain.

It has been demonstrated that the AP2/ERF proteins have important functions in the transcriptional regulation of a variety of biological processes related to growth and development, as well as various responses to environmental stimuli.

After finding the tobacco ERFs, many proteins in the ERF family were identified and implicated in many diverse functions in cellular processes, such as hormonal signal transduction, response to biotic and abiotic stresses, regulation of metabolism, and in developmental processes in various plant species.

Toshitsugu Nakano, Kaoru Suzuki, Tatsuhito Fujimura, and Hideaki Shinshi.
Genome-wide analysis of the ERF gene family in Arabidopsis and rice.
Plant Physiol, 2006. 140(2): p. 411-32.
PMID: 16407444

The first class are proteins which bind to ethylene response elements (ERE) or GCC boxes (tobacco EREBPs, Arabidopsis AtEBP and AtERF1-5, and tomato Pti4-6) found in the promoters of ethylene-inducible pathogenesis related genes. The GCC box is an 11 bp sequence (TAAGAGCCGCC) with a core GCCGCC sequence that is required for binding.
The second class includes proteins that bind to the C-repeat or dehydration response element (DRE) in the promoters of genes that are turned on in response to low temperatures and/or water deficit (CBF1, CBF2, CBF3/DREB1A and DREB2A). The C-repeat/DREs contain the core sequence CCGAC.

Nole-Wilson S, Krizek BA.
DNA binding properties of the Arabidopsis floral development protein AINTEGUMENTA.
Nucleic Acids Res. 2000 Nov 1;28(21):4076-82. Erratum in: Nucleic Acids Res 2001 Mar 1;29(5):1261.
PMID: 11058102