Biophysical properties of regions flanking the bHLH-Zip motif in the p22 Max protein.
The Max protein is the central dimerization partner in the Myc-Max-Mad network of transcriptional regulators, and a founding structural member of the family of basic-helix-loop-helix (bHLH)-leucine zipper (Zip) proteins. Biologically important regions flanking its bHLH-Zip motif have been disordered or absent in crystal structures. The present study shows that these regions are resistant to proteolysis in both the presence and absence of DNA, and that Max dimers containing both flanking regions have significantly higher helix content as measured by circular dichroism than that predicted from the crystal structures. Nuclear magnetic resonance measurements in the absence of DNA also support the inferred structural order. Deletion of both flanking regions is required to achieve maximal DNA affinity as measured by EMSA. Thus, the previously observed functionalities of these Max regions in DNA binding, phosphorylation, and apoptosis are suggested to be linked to structural properties.
Pursglove
Sharon E
SE
Medical Biochemistry and Biophysics, Karolinska Institutet, 171 77 Stockholm, Sweden.
Fladvad
Malin
M
Bellanda
Massimo
M
Moshref
Ahmad
A
Henriksson
Marie
M
Carey
Jannette
J
Sunnerhagen
Maria
M
D024509:3' Flanking Region / Q000235:genetics; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D017100:Bacteriophage P22 / Q000378:metabolism; D050976:Basic-Leucine Zipper Transcription Factors; D001665:Binding Sites; D004279:DNA, Viral / Q000737:chemistry*; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics; D024202:Electrophoretic Mobility Shift Assay / Q000379:methods*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry* / Q000235:genetics; D013329:Structure-Activity Relationship; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics
D050976:Basic-Leucine Zipper Transcription Factors; D004279:DNA, Viral; D004268:DNA-Binding Proteins; C067850:Myc associated factor X; D011994:Recombinant Proteins; D014157:Transcription Factors