National Center for
1FU6: NMR STRUCTURE OF THE N-SH2 DOMAIN OF THE P85 SUBUNIT OF PI3-KINASE
NMR structure of the N-SH2 of the p85 subunit of phosphoinositide 3-kinase complexed to a doubly phosphorylated peptide reveals a second phosphotyrosine binding site
Biochemistry (2000) 39 p.15860-15869
The N-terminal src homology 2 (SH2) domain of the p85 subunit of phosphoinositide 3-kinase (PI3K) has a higher affinity for a peptide with two phosphotyrosines than for the same peptide with only one. This unexpected result was not observed for the C-terminal SH2 from the same protein. NMR structural analysis has been used to understand the behavior of the N-SH2. The structure of the free SH2 domain has been compared to that of the SH2 complexed with a doubly phosphorylated peptide derived from polyomavirus middle T antigen (MT). The structure of the free SH2 domain shows some differences from previous NMR and X-ray structures. In the N-SH2 complexed with a doubly phosphorylated peptide, a second site for phosphotyrosine interaction has been identified. Further, line shapes of NMR signals showed that the SH2 protein-ligand complex is subject to temperature-dependent conformational mobility. Conformational mobility is also supported by the spectra of the ligand peptide. A binding model which accounts for these results is developed.