INVESTIGADORES
GONZALEZ Daniel Hector
artículos
Título:
Positively charged residues at the N-terminal arm of the homeodomain are required for efficient DNA binding by homeodomain-leucine zipper proteins
Autor/es:
PALENA, CLAUDIA M.; TRON, ADRIANA E.; BERTONCINI, CARLOS W.; GONZALEZ, DANIEL H.; CHAN, RAQUEL L.
Revista:
JOURNAL OF MOLECULAR BIOLOGY
Editorial:
ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD
Referencias:
Lugar: Manchester; Año: 2001 vol. 308 p. 39 - 47
ISSN:
0022-2836
Resumen:
Plant homeodomain-leucine zipper proteins, unlike most animal
homeodomains, bind DNA efficiently only as dimers. In the present work,
we report that the deletion of the homeodomain N-terminal arm (first
nine residues) of the homeodomain-leucine zipper protein Hahb-4
dramatically affects its DNA-binding affinity, causing a 70-fold
increase in dissociation constant. The addition of the N-terminal arm of
Drosophila Antennapedia to the truncated form restores the DNA-binding
affinity of dimers to values similar to those of the native form.
However, the Antennapedia N-terminal arm is not able to confer increased
binding affinity to monomers of Hahb-4 lacking the leucine zipper
motif, indicating that the inefficient binding of monomers must be due
to structural differences in other parts of the molecule. The
construction of proteins with modifications at residues 5 to 7 of the
homeodomain suggests strongly that positively charged amino acids at
these positions play essential roles in determining the DNA-binding
affinity. However, the effect of mutations at positions 6 and 7 can be
counteracted by introducing a stretch of positively charged residues at
positions 1 to 3 of the homeodomain. Sequence comparisons indicate that
all homeodomain-leucine zipper proteins might use contacts of the
N-terminal arm with DNA for efficient binding. The occurrence of a
homeodomain with a DNA-interacting N-terminal arm must then be an
ancient acquisition in evolution, earlier than the separation of lines
leading to metazoa, fungi and plants.