Phosphorylation of Tomato 1-Aminocyclopropane-1-carboxylic Acid Synthase, LE-ACS2, at the C-terminal Region

Miho Tatsuki, Hitoshi Mori
2001 Journal of Biological Chemistry  
1-Aminocyclopropane-1-carboxylic acid synthase is a key enzyme in the ethylene biosynthesis pathway. Recent studies raise the possibility that 1-aminocyclopropane-1-carboxylic acid synthase (ACS) is regulated not only transcriptionally but also post-translationally. To elucidate post-translational ACS regulation, we analyzed the modification of LE-ACS2 protein, a woundinducible isozyme in the ACS family, in tomato fruit (Lycopersicon esculentum L.) using an anti-LE-ACS2 antibody. We detected
more » ... ody. We detected phosphorylated LE-ACS2 at 55-kDa using immunoprecipitation from an extract of wounded fruit fed with [ 32 P]inorganic phosphate. Analysis of LE-ACS2 phosphoamino acids indicated that serine residue(s) were phosphorylated. In vitro phosphorylation analyses using site-directed mutagenesis of recombinant LE-ACS2 as a substrate demonstrate that serine 460 located at the C-terminal region of ACS is phosphorylated. During tomato ripening stages, expression of both LE-ACS2 and LE-ACS4 mRNA increased. LE-ACS4, however, was not phosphorylated in vitro. These results suggest that ACS isozymes have different post-translational regulatory mechanisms, such as phosphorylation. Brilliant Blue; PP2A, protein phosphatase 2A; -PPase, protein phosphatase; MOPS, 4-morpholinepropanesulfonic acid.
doi:10.1074/jbc.m101543200 pmid:11375393 fatcat:w4owath2znhztfzrrpm7nzjkdm