PROSITE documentation PDOC51297
K-box domain profile


MADS genes in plants encode key developmental regulators of vegetative and reproductive development. The majority of the plant MADS proteins share a stereotypical MIKC structure. It comprises (from N- to C-terminal) an N-terminal domain, which is, however, present only in a minority of proteins; a MADS domain (see <PDOC00302>), which is the major determinant of DNA-binding but which also performs dimerization and accessory factor binding functions; a weakly conserved intervening (I) domain, which constitutes a key molecular determinant for the selective formation of DNA-binding dimers; a keratin-like (K-box) domain, which promotes protein dimerization; and a C-terminal (C) domain, which is involved in transcriptional activation or in the formation of ternary or quaternary protein complexes. The 80-amino acid K-box domain was originally identified as a region with low but significant similarity to a region of keratin, which is part of the coiled-coil sequence constituting the central rod-shaped domain of keratin [1,2,3].

The K-box protein-protein interaction domain which mediates heterodimerization of MIKC-type MADS proteins contains several heptad repeats in which the first and the fourth positions are occupied by hydrophobic amino acids suggesting that the K-box domain forms three amphipathic α-helices referred to as K1, K2, and K3 [3].

The profile we developed covers the entire K-box domain.

Last update:

February 2007 / First entry.


Technical section

PROSITE method (with tools and information) covered by this documentation:

K_BOX, PS51297; K-box domain profile  (MATRIX)


1AuthorsAlvarez-Buylla E.R. Pelaz S. Liljegren S.J. Gold S.E. Burgeff C. Ditta G.S. Ribas de Pouplana L. Martinez-Castilla L. Yanofsky M.F.
TitleAn ancestral MADS-box gene duplication occurred before the divergence of plants and animals.
SourceProc. Natl. Acad. Sci. U.S.A. 97:5328-5333(2000).
PubMed ID10805792

2AuthorsHenschel K. Kofuji R. Hasebe M. Saedler H. Muenster T. Theissen G.
TitleTwo ancient classes of MIKC-type MADS-box genes are present in the moss Physcomitrella patens.
SourceMol. Biol. Evol. 19:801-814(2002).
PubMed ID12032236

3AuthorsYang Y. Fanning L. Jack T.
TitleThe K domain mediates heterodimerization of the Arabidopsis floral organ identity proteins, APETALA3 and PISTILLATA.
SourcePlant J. 33:47-59(2003).
PubMed ID12943540

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