title: Dimerization and DNA binding facilitate alpha-helix formation of Max in solution.
abstract: Max is a basic region/helix-loop-helix/leucine zipper (b/HLH/Z) protein that forms a hetero-complex with the Myc family proteins Myc, Mad, and Mxi1, and a homo-complex with itself. These complexes specifically bind to double-stranded DNA containing CACGTG sequences. Here, we report on the structural properties in aqueous solution of a 109-amino-acid protein, Max110, corresponding to the N-terminal domain of Max containing the b/HLH/Z motif (residues 2-110), as characterized by combined use of circular dichroism (CD) and sedimentation equilibrium experiments. The results showed that the alpha-helical content of Max110 increases with increasing protein concentration. The sedimentation equilibrium data indicated that Max110 exists as a monomer at low protein concentration, and forms a dimer at high protein concentration. Further increases in the alpha-helical content of Max110 occur upon addition of DNA with the CACGTG recognition sequence. Thus, dimerization and binding to DNA of Max both favor an increase of the alpha-helical content.
authors.affiliation: Department of Bioengineering, Faculty of Engineering, Yokohama National University.
authors.forename: M
authors.initials: M
authors.lastname: Horiuchi
authors.forename: Y
authors.initials: Y
authors.lastname: Kurihara
authors.forename: M
authors.initials: M
authors.lastname: Katahira
authors.forename: T
authors.initials: T
authors.lastname: Maeda
authors.forename: T
authors.initials: T
authors.lastname: Saito
authors.forename: S
authors.initials: S
authors.lastname: Uesugi
mesh_terms: D000595:Amino Acid Sequence; D050976:Basic-Leucine Zipper Transcription Factors; D002942:Circular Dichroism; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D019281:Dimerization; D018257:Helix-Loop-Helix Motifs; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012996:Solutions; D014157:Transcription Factors
chemical_list: D050976:Basic-Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; C067850:Myc associated factor X; D011994:Recombinant Proteins; D012996:Solutions; D014157:Transcription Factors; D004247:DNA