This invention concerns new configurations for biological switches and provides new methods and materials useful for regulating biological events in animal cells. The invention involves recombinant DNA constructs comprising DNA sequences derived from sequences encoding the proteins FRAP, Tor1, Tor2 and other proteins capable of binding to FKBP:rapamycin, other recombinant DNA constructs comprising DNA sequences encoding part or all of an FKBP protein, the proteins encoded by those constructs, cells (especially animal cells) transformed with one or more of the constructs, small molecules (multivalent multimerizing agents) which bind to and are capable of inducing multimerization of the chimeric proteins, and methods for preparing and using the foregoing.