Expression and purification of the DNA-binding domain of the human transcription factor E2F1

The DNA-binding domain of the human transcription factor E2F1 was expressed in Escherichia coli. Through a single purification step using a Ni2+ column, 40-50 mg of the highly purified recombinant protein was obtained from 1 liter of bacterial culture. In addition, it was shown that the recombinant protein had higher stability and solubility under acidic conditions than at a neutral or alkaline pH. The gel shift assay showed that the recombinant E2F1 DNA-binding domain was active in binding a fragment containing E2F sites. Circular dichroism measurements revealed that the recombinant protein approximately contains 33% alpha-helix, 11% beta-sheet, 5% turn, and 51% random coil at pH 7.0, and there was no obvious change for the secondary structure of the recombinant protein between pH 4.0 and pH 9.0. A 3D model was obtained by comparative protein modeling with a homologous protein whose structure was known by program Modeller 4. With the program DSSP, the predicted secondary structure content of the model was consistent with the result of circular dichroism spectrum.

Proton NMR investigation of heme and surrounding proton in low-spin cyanide-ligated bacterial hemoglobin from Vitreoscilla

(1)H NMR spectra of low-spin cyanide-ligated bacterial hemoglobin from Vitreoscilla (VtHb-CN) are reported. The assignments of the(1)H NMR spectra of VtHb-CN have been made through MCOSY, NOESY, 1D TOE and SUPERWEFT experiments. Almost all resonance peaks of heme and ligated His85 are identified. The spin-lattice relaxation time T (1)'s and the variation relationships of chemical shifts of these peaks with temperature have been acquired, from which the distances between the measured protons and Fe(3+), and the diamagnetic chemical shifts have been acquired, respectively. The ionization constants of pK (a)'s of ligated His85 are determined through pH titration of chemical shift, which is 4.95 for ligated His85 C(2)H proton. The lower pK (a) is attributed to the influence of the Fe(3+) of carrying positive charge and the coordination of His85 and Fe(3+) of heme.

Solution structure of a fragment of the dimerization domain of DP-1 determined by 1H-nuclear magnetic resonance and distance geometry

The structure of a synthesized peptide with the sequence of NHILPNESAYDQKNIRRRVYDALNVLMAMNIISK that corresponds to residues 151-184 of transcription factor DP-1 (Girling et al., Nature 362 (1993) 83-87) was determined by 1H-nuclear magnetic resonance in water and 40% d3-trifluoroethanol/water, respectively. Nuclear Overhauser effect cross peaks, alphaH chemical shifts and J-coupling constants of alphaH-NH show that the peptide consists a helix from Ser-8 to Ser-33 in solution. Fifty structures were constructed with 288 upper distance limits and 21 angle constraints by DIANA (Guntert et al., J. Mol. Biol. 217 (1991) 517-530). Although the N-terminal of the peptide exhibits a random conformation, the 20 best structures show a root mean square deviation of 0.89+/-0.36 A for backbone atoms and 1.80+/-0.34 A for heavy atoms from residue Ser-8 to Ser-33. This result supports the proposal that DP-1 and E2F-1 may dimerize with a coiled-coil type interaction.

Solution structure of a fragment of the dimerization domain of E2F-1 determined by circular dichroism, 1H nuclear magnetic resonance and distance geometry

The structure of a synthesized peptide with the sequence GVVDLNWAAEVLKVQKRRIYDITNVLEGIQ which corresponds to residues 149-178 of transcription factor E2F-1 was determined by 1H nuclear magnetic resonance in 40% d3-TFE/water. NOE cross peaks and alphaH chemical shifts indicate that the peptide consists of a helix from Ala-8 to Leu-26 in this solution. Circular dichroism measurements confirm the presence of nearly 45% helix in TFE/water solution but show no evidence of helicity in water solution of this peptide. Fifty structures were constructed with 329 upper distance limits by DIANA. The 20 best conformers show a RMSD of 0.78 A for backbone atoms and 1.78 A for heavy atoms from residue Ala-8 to Leu-26. This result, together with our previous work on the solution structure of a fragment of DP-1, supports the proposal that E2F-1 and DP-1 may dimerize with a coiled-coil type interaction.

[Relationship of atopic dermatitis to residential environment. A study of the comparison between diagnosis by medical examination and assessment by questionnaire]

Diagnosis of atopic dermatitis (AD) according to criterion of the Japanese Dermatology Society by medical examination and a questionnaire survey concerning the living environment and presence of allergic diseases were performed on 1725 elementary school children living in Hirosaki-city and its suburbs in Aomiri Prefecture. In addition a scratch test for mite antigen was conducted 523 of the children and a patch test on 240. No difference was found between the rate of children diagnosed as having AD during the medical examination which was 12.9%, and the rate of children who responded as presently having AD in the questionnaire which was 12.8%. However the rate of concordance between those diagnosed to have AD by medical examination and the group that responded as having AD in the questionnaire was about 50%. For AD in children diagnosed by medical examination, a residential environment of the houses that there were moldy and leaking appeared to be a risk factor. Risk factors of children with AD from the questionnaire survey appeared to be houses built within 20 years. Clearly there were differences in conclusions regarding risk factor between the medical examination and the questionnaire. In terms of increasing reliability, a medical examination would be preferred. From the results of allergic tests, the children who lived in houses built within 20 years had a high response to the patch test. These results suggest that houses that are moldy and leaking, or built within 20 years may be considered to be risk factors for outbreak of AD.