The structure of Antirrhinum centroradialis protein (CEN) suggests a role as a kinase regulator

Expression of the plant protein centroradialis (CEN) leads to a morphologic al switch between shoot growth and the development of flower structures (in florescence). We have determined the crystal structure of Antirrhinum CEN t o 1.9 Angstrom resolution. This structure confirms the CEN proteins as a su bset of the family of phosphatidylethanolamine-binding proteins (PEBP), as predicted from sequence homology. Mammalian forms of PEEP have been found t o act as inhibitors of MAP kinase signalling, a central signalling cascade regulating cell differentiation. CEN and PEEP proteins share a similar topo logy dominated by a large central beta-sheet. The strong conservation of a binding pocket at one end of this sheet which is capable of binding phospho ryl ligands, suggests the biological effects of CEN, like PEEP, arise from the ability of this region to form complexes with phosphorylated ligands, h ence interfering with kinases and their effecters. (C) 2000 Academic Press.