A DNA binding protein with an M(r) of 1 1000 was purified from Ustilag
o maydis. Its solubility in acid, amino acid composition, and mobility
during gel electrophoresis are reminiscent of properties observed for
the high mobility group nonhistone chromosomal proteins. The protein
recognizes cruciform DNA made from oligonucleotides and also binds pre
ferentially to a plasmid containing an extruded cruciform.