Influence of FK506 on the interaction of C1q-C with FKBP13. Yeast L40 was cotransformed with pBTM-FKBP13w/oS and with pGAD-C1q-Cw/oS. Cotransformants were incubated in the presence or absence of FK506 and analyzed as described in material and methods. Shown are the results of 4–8 independent experiments ± S.E.M.. The control (absence of FK506) was defined as 100 %; the solvent ethanol was without influence.