Solution structure of the B-Myb DNA-binding domain: a possible role for conformational instability of the protein in DNA binding and control of gene expression.
Double- and triple-resonance heteronuclear NMR spectroscopy have been used to determine the high-resolution solution structure of the minimal B-Myb DNA-binding domain (B-MybR2R3) and to characterize the specific complex formed with a synthetic DNA fragment corresponding to the Myb target site on the Myb-regulated gene tom-1. B-MybR2R3 is shown to consist of two independent protein domains (R2 and R3) joined by a short linker, which have strikingly different tertiary structures despite significant sequence similarities. In addition, the C-terminal region of B-Myb R2 is confirmed to have a poorly defined structure, reflecting the existence of multiple conformations in slow to intermediate exchange. This contrasts with the tertiary structure reported for c-MybR2R3, in which both R2 and R3 have the same fold and the C-terminal region of R2 forms a stable, well-defined helix [Ogata, K., et al. (1995) Nat. Struct. Biol. 2, 309-320]. The NMR data suggest there are extensive contacts between B-MybR2R3 and its DNA target site in the complex and are consistent with a significant conformational change in the protein on binding to DNA, with one possibility being the formation of a stable helix in the C-terminal region of R2. In addition, conformational heterogeneity identified in R2 of B-MybR2R3 bound to the tom-1-A target site may play an important role in the control of gene expression by Myb proteins.
McIntosh
P B
PB
Laboratory of Molecular Structure, National Institute for Biological Standards and Control, Potters Bar, UK.
Frenkiel
T A
TA
Wollborn
U
U
McCormick
J E
JE
Klempnauer
K H
KH
Feeney
J
J
Carr
M D
MD
D000818:Animals; D001665:Binding Sites; D018797:Cell Cycle Proteins; D018360:Crystallography, X-Ray; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D046911:Macromolecular Substances; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D009857:Oncogenes; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism; D020598:Proto-Oncogene Proteins c-myb; D017386:Sequence Homology, Amino Acid; D012996:Solutions; D015534:Trans-Activators / Q000737:chemistry / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; D011518:Proto-Oncogene Proteins; D020598:Proto-Oncogene Proteins c-myb; D012996:Solutions; D015534:Trans-Activators; D014157:Transcription Factors; D004247:DNA