Structure of murine Tcl1 at 2.5 angstrom resolution and implications for the TCL oncogene family

Tcl1 and Mtcp1, members of the Tcl1 family, are implicated in T-cell prolym phocytic leukemia. The crystal structure of a dimer of murine Tcl1 has been determined at 2.5 Angstrom resolution with an R factor of 0.225. Murine Tc l1, human Tcl1 and Mtcp1 share very similar subunit structures, with RMS di fferences of 0.6 and 1.4 Angstrom for C-alpha atoms, respectively, while th e sequences share 50 and 36% identity, respectively. These structures fold into an eight-stranded beta -barrel of unique topology and high internal sy mmetry of 1.1-1.3 Angstrom for the two halves of human and murine Tcl1 and 1.7 Angstrom for Mtcp1, despite the low 12-13% sequence identity. The molec ular surfaces of all three structures showed a common planar region which i s likely to be involved in protein-protein interactions.