O. Frank et al., PROTEIN FOOTPRINTING REVEALS SPECIFIC BINDING MODES OF A HIGH-MOBILITY GROUP PROTEIN-I TO DNAS OF DIFFERENT CONFORMATION, The Journal of biological chemistry, 273(32), 1998, pp. 20015-20020
The high mobility group proteins I and Y (HMGI/Y) are abundant compone
nts of chromatin. They are thought to derepress chromatin, affect the
assembly and activity of the transcriptional machinery, and associate
with constitutive heterochromatin during mitosis. HMGI/Y protein molec
ules contain three potential DNA-binding. motifs (AT-hooks), but the e
xtent of contacts between DNA and the entire protein has not been dete
rmined, We have used a protein-footprinting procedure to map regions o
f the Chironomus HMGI protein molecule that are involved in contacts w
ith DNA, We find that in the presence of double-stranded DNA all AT-ho
ok motifs are protected against hydroxyl radical proteolysis. In contr
ast, only two motifs were protected in the presence of four-wag juncti
on DNA. Large regions that flank the AT-hook motifs were found to be s
trongly protected against proteolysis in complexes with interferon-bet
a promoter DNA, suggesting amino acid residues outside the AT-hooks co
nsiderably contribute to DNA binding.