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The TCP domain has been named after its first characterized members (TB1, CYC
and PCFs). So far, members of the TCP family have only been found in plants
and function in processes related to cell proliferation. The TCP domain is
probably involved in DNA-binding and protein-protein interactions .
The TCP domain is predicted to form a non-canonical basic-Helix-Loop-Helix
(bHLH). The main conserved features of the TCP domain are: two short stretches
of residues in the basic region, hydrophobic residues along the apolar face of
both α-helices, a tryptophan in helix II, and a helix-breaking glycine in
the loop between the helices. However the residues in the loop and the
hydrophilic residues of the helices are not as well conserved. TCP domains
form two subfamilies: one closely related to CYC and TB1, and another more
related to the PCFs. The basic region of the CYC/TB1 subfamily contains a
putative bipartite nuclear localization signal (NLS) (see <PDOC00015>) while
the basic region of the PCF subfamily contains only a portion of a bipartite
Some proteins known to contain a TCP domain are listed below:
Antirrhinum majus cycloidea (cyc). It is involved in the control of floral
symmetry, a character that has changed many times during plant evolution.
Maize teosinte branched 1 (tb1). It controls developmental switches that
contributed to the evolution of maize from its wild ancestor teosinte.
Rice PCF1 and PCF2, proteins that may bind to DNA as homo- or heterodimers.
These proteins were isolated on the basis of their ability to bind
specifically to promoter elements of the rice gene for the proliferating
cell nuclear antigen, PCNA, a protein involved in DNA replication and cell
Arabidopsis thaliana TCP2 and TCP3, which correlate with actively dividing
regions of the floral meristem.
The profile we developed covers the entire TCP domain.
February 2008 / First entry.
PROSITE method (with tools and information) covered by this documentation:
Cubas P., Lauter N., Doebley J., Coen E.
The TCP domain: a motif found in proteins regulating plant growth and development.
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