    2.4.1.18 | phosphoprotein |
native and recombinant maize SBEIIb are used as substrates for amyloplast protein kinases to identify phosphorylation sites on the protein, bioinformatics, site-directed mutagenesis, and mass spectrometry identify three phosphorylation sites at Ser residues: Ser649, Ser286, and Ser297. Ca2+-dependent protein kinases from amyloplasts, termed K1, responsible for Ser649 and Ser286 phosphorylation, and K2, responsible for Ser649 and Ser297 phosphorylation. The Ser286 and Ser297 phosphorylation sites are conserved in all plant branching enzymes and are located at opposite openings of the 8-stranded parallel beta-barrel of the active site, which is involved with substrate binding and catalysis. Molecular dynamics simulation analysis indicates that phospho-Ser297 forms a stable salt bridge with Arg665, part of a conserved Cys-containing domain in plant branching enzymes. Ser649 conservation appears confined to the enzyme in cereals and is not universal, and is presumably associated with functions specific to seed storage |
-, 736465 |
