Conformational changes in the PBX homeodomain and C-terminal extension upon binding DNA and HOX-derived YPWM peptides.
PBX is a member of the three amino acid loop extension (TALE) class of homeodomains. PBX binds DNA cooperatively with HOX homeodomain proteins that contain a conserved YPWM motif. The amino acids immediately C-terminal to the PBX homeodomain increase the affinity of the homeodomain for its DNA site and HOX proteins. We have determined the structure of the free PBX homeodomain using NMR spectroscopy. Both the PBX homeodomain and the extended PBX homeodomain make identical contacts with a 5'-TGAT-3' DNA site and a YPWM peptide. A fourth alpha-helix, which forms upon binding to DNA, stabilizes the extended PBX structure. Variations in DNA sequence selectivity of heterodimeric PBX-HOX complexes depend on the HOX partner; however, a comparison of five different HOX-derived YPWM peptides showed that each bound to PBX in the same way, differing only in the strength of the association.
Sprules
T
T
Department of Biochemistry, McGill Cancer Centre and Montreal Joint Centre for Structural Biology, McIntyre Medical Sciences Building, McGill University, 3655 Drummond, Montreal, PQ, Canada, H3G 1Y6.
Green
N
N
Featherstone
M
M
Gehring
K
K
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001665:Binding Sites; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D010455:Peptides / Q000378:metabolism*; D000075062:Pre-B-Cell Leukemia Transcription Factor 1; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011518:Proto-Oncogene Proteins / Q000737:chemistry* / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D000099261:Homeobox A1 Protein
D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D010446:Peptide Fragments; D010455:Peptides; D000075062:Pre-B-Cell Leukemia Transcription Factor 1; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; D000099261:Homeobox A1 Protein; C083400:PBX1 protein, human