STRUCTURE OF THE ETS-1 POINTED DOMAIN AND MITOGEN-ACTIVATED PROTEIN-KINASE PHOSPHORYLATION SITE

The Pointed (PNT) domain and an adjacent mitogen-activated protein (MA P) kinase phosphorylation site are defined by sequence conservation am ong a subset of ets transcription factors and are implicated in two re gulatory strategies, protein interactions and posttranslational modifi cations, respectively. By using NMR, we have determined the structure of a 110-residue fragment of murine Ets-1 that includes the PNT domain and MAP kinase site. The Ets-1 PNT domain forms a monomeric five-heli x bundle. The architecture is distinct from that of any known DNA- or protein-binding module, including the helix-loop-helix fold proposed f or the PNT domain of the ets protein TEL. The MAP kinase site is in a highly flexible region of both the unphosphorylated and phosphorylated forms of the Ets-1 fragment. Phosphorylation alters neither the struc ture nor monomeric state of the PNT domain. These results suggest that the Ets-1 PNT domain functions in heterotypic protein interactions an d support the possibility that target recognition is coupled to struct uring of the MAP kinase site.