REFINED SOLUTION STRUCTURE AND DYNAMICS OF THE DNA-BINDING DOMAIN OF THE HEAT-SHOCK FACTOR FROM VEROMYCES LACTIS

The solution structure of the 92 residue (11 kDa) winged helix-turn-he lix DNA-binding domain from the kluyveromyces lactis heat shock factor was refined using a total of 932 NOE, 35 phi, 25 chi 1, 5 chi 2 and 4 4 hydrogen bond restraints. The overall root-mean-square deviation for structured regions was 0.75(+/-0.15) Angstrom. The three-helix bundle and four-stranded beta-sheet are well defined. with rmsd of 0.53(+/-0 .10) Angstrom and 0.60(+/-0.17) Angstrom, respectively Helix H2 is und erwound and bent near Pro45. The angle between helix H2 and the propos ed recognition helix H3 is 96(+/-6)degrees. Detailed comparisons are m ade with the X-ray structure of this protein as well as other structur al studies on HSF. Overall, the results are consistent with the earlie r studies. Differences are related to protein-protein interactions in the crystal and dynamics in solution. Backbone dynamics was investigat ed via N-15 relaxation. The average R(1), R(2) and NOE values for resi dues in segments of secondary structure were 1.9(+/-0.9) s(-1), 7.8(+/ -0.9) s(-1) and 0.81(+/-0.05), respectively. The correlation time base d on these data was 5.6(+/-0.4) ns. Motional order parameters were cal culated by fitting the relaxation data to one of three models. Low-ord er parameters were found for residues that comprise the turn between h elices H2 and H3 (residues Lys49 to Phe53), and most strikingly the 16 residue wing (residues Val68 to Arg83). These data are consistent wit h the lack of long-range NOEs identified in these regions. The data pr ovide a basis for comparison with results of the protein-DNA complex. The relationship between structure and function is discussed. (C) 1995 Academic Press Limited