PARTICLE-BOUND AUXIN RECEPTOR FROM TOBACCO PITH CALLUS

The binding of NAA to particulate fractions isolated from tobacco pith callus was studied. The presence of a specific auxin receptor with high affinity was demonstrated. NAA-binding was maximal after 30 min of incubation at 36°C (pH 5). The affinity constant for NAA was approx. 3 × 106/mol and the concentration of binding-sites was approx. 75 pmol/g fresh weight (60 pmol/mg protein). The affinities for various auxin analogues were roughly correlated with their activities in auxin bio-assays. The same type of receptor was found in freshly excised tobacco pith, but at a lower concentration. © 1979.