No abstract

Tcl1 and Mtcp1, members of the Tcl1 family, are implicated in T-cell prolymphocytic leukemia. The crystal structure of a dimer of murine Tcl1 has been determined at 2.5 A Ê resolution with an R factor of 0.225. Murine Tcl1, human Tcl1 and Mtcp1 share very similar subunit structures, with RMS differences of 0.6 and 1.4 A Ê for C atoms, respectively, while the sequences share 50 and 36% identity, respectively. These structures fold into an eight-stranded -barrel of unique topology and high internal symmetry of 1.1±1.3 A Ê for the two halves of human and murine Tcl1 and 1.7 A Ê for Mtcp1, despite the low 12±13% sequence identity. The molecular surfaces of all three structures showed a common planar region which is likely to be involved in protein±protein interactions.