Structural details on mdm2-p53 interaction.
Mdm2 is a cellular antagonist of p53 that keeps a balanced cellular level of p53. The two proteins are linked by a negative regulatory feedback loop and physically bind to each other via a putative helix formed by residues 18-26 of p53 transactivation domain (TAD) and its binding pocket located within the N-terminal 100-residue domain of mdm2 (Kussie, P. H., Gorina, S., Marechal, V., Elenbaas, B., Moreau, J., Levine, A. J., and Pavletich, N. P. (1996) Science 274, 948-953). In a previous report we demonstrated that p53 TAD in the mdm2-freee state is mostly unstructured but contains two nascent turns in addition to a "preformed" helix that is the same as the putative helix mediating p53-mdm2 binding. Here, using heteronuclear multidimensional NMR methods, we show that the two nascent turn motifs in p53 TAD, turn I (residues 40-45) and turn II (residues 49-54), are also capable of binding to mdm2. In particular, the turn II motif has a higher mdm2 binding affinity ( approximately 20 mum) than the turn I and targets the same site in mdm2 as the helix. Upon mdm2 binding this motif becomes a well defined full helix turn whose hydrophobic face formed by the side chains of Ile-50, Trp-53, and Phe-54 inserts deeply into the helix binding pocket. Our results suggest that p53-mdm2 binding is subtler than previously thought and involves global contacts such as multiple "non-contiguous" minimally structured motifs instead of being localized to one small helix mini-domain in p53 TAD.
Chi
Seung-Wook
SW
Protein Analysis and Design Laboratory, Division of Drug Discovery, Korea Research Institute of Bioscience and Biotechnology, Yusong P. O. Box 115, Daejon 305-600, Korea.
Lee
Si-Hyung
SH
Kim
Do-Hyoung
DH
Ahn
Min-Jung
MJ
Kim
Jae-Sung
JS
Woo
Jin-Young
JY
Torizawa
Takuya
T
Kainosho
Masatsune
M
Han
Kyou-Hoon
KH
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D002461:Cell Line, Transformed; D006801:Humans; D007700:Kinetics; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D051736:Proto-Oncogene Proteins c-mdm2 / Q000737:chemistry* / Q000378:metabolism; D013053:Spectrophotometry; D020349:Surface Plasmon Resonance; D013997:Time Factors; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
D008024:Ligands; D010455:Peptides; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D051736:Proto-Oncogene Proteins c-mdm2