Nature 395, 863–869 (1998)

D.O.F.'s full address should have included the Institut für Zoophysiologie und Zellbiologie (University of Potsdam, Lennéstrasse 7a, 14471 Potsdam, Germany); lane 1 of Fig. 5a referred to transfected kin4 (not in4); and in Fig. 6b, the panels referred to as “top” and “bottom” should have been left and right panels, respectively.