14-3-3 Proteins and a 13-lipoxygenase form associations in a phosphorylation-dependent manner

Recently, we have demonstrated by two different methods that lipoxgenases ( LOXs) and 14-3-3 proteins form interactions in barley embryos [Holtman, Rob erts, Oppedijk, Testerink, van Zeijl and Wang (2000) FEES Lett. 474, 48-52] . It was shown by both co-immunoprecipitations and surface-plasmon resonanc e experiments that 13-LOX, but not 9-LOX, forms interactions with 14-3-3 pr oteins. In the present report we show that the presence of 13-LOX and 14-3- 3 proteins was established in high-molecular-mass complexes. Amounts of 13- LOX and 14-3-3 proteins in high-molecular-mass fractions increased during g ermination, but were reduced after dephosphorylation of protein extracts or competition with the 14-3-3-binding peptide P-Raf-259, indicating that 13- LOX and 14-3-3 proteins interact in a phosphorylation-dependent manner.