MRC Laboratory for Molecular Cell Biology and Department of Biochemistry, University College London, Gower Street, London WC1E 6BT, UK. alison.lloyd@ucl.ac.uk
The Ras/Raf/MEK/ERK signaling pathway is one of the best understood signal routes in cells. Recent studies add complexity to this cascade by indicating that the two ERK kinases, ERK1 (p44ERK1) and ERK2 (p42ERK2), may have distinct functions.