Oligomeric structure of the human EphB2 receptor SAM domain

The sterile alpha motif (SAM) domain is a protein interaction module that i s present in diverse signal-transducing proteins. SAM domains are known to form homo- and hetero-oligomers. The crystal structure of the SAM domain fr om an Eph receptor tyrosine kinase, EphB2, reveals two Large interfaces. In one interface, adjacent monomers exchange amino-terminal peptides that ins ert into a hydrophobic groove on each neighbor. A second interface is compo sed of the carboxyl-terminal helix and a nearby Loop. A possible oligomer, constructed from a combination of these binding modes, may provide a platfo rm for the formation of larger protein complexes.