Assignment of the auxin binding abilities of ABP44 in gel

Several approaches were successfully performed to directly assign and characterize auxin binding of ABP44 in gel. The 44 kDa high affinity auxin binding protein ABP44 from pea was tested for its ability to bind 5-azido-[7-3H]-IAA in photoaffinity labeling experiments. Competition experiments with several auxin analogues confirm data published previously (Reinard and Jacobsen 1995). Critical reflections of the limitations of the method are also discussed. Immunostaining using the antibody D16 (Napier and Venis 1992), which is directed against the putative binding site of ABP1, revealed that ABP44's auxin binding site is at least partially related to the corresponding site of ABP1. Nevertheless, both proteins do not share any further immunological relationships. Our results with D16 recommend a careful reconsideration of data published by other authors. Furthermore, a 80 kDa, dimeric glutathione dependent formaldehyde dehydrogenase (FDH) from mung bean, described recently, was found to be different from ABP44. In contrast to the described FDH, ABP44 exhibited no FDH activity.