PMID:17601822

Citation	Taoka, K, Ham, BK, Xoconostle-Cázares, B, Rojas, MR and Lucas, WJ (2007) Reciprocal phosphorylation and glycosylation recognition motifs control NCAPP1 interaction with pumpkin phloem proteins and their cell-to-cell movement. Plant Cell 19:1866-84
Abstract	In plants, cell-to-cell trafficking of non-cell-autonomous proteins (NCAPs) involves protein-protein interactions, and a role for posttranslational modification has been implicated. In this study, proteins contained in pumpkin (Cucurbita maxima cv Big Max) phloem sap were used as a source of NCAPs to further explore the molecular basis for selective NCAP trafficking. Protein overlay assays and coimmunoprecipitation experiments established that phosphorylation and glycosylation, on both Nicotiana tabacum NON-CELL-AUTONOMOUS PATHWAY PROTEIN1 (Nt-NCAPP1) and the phloem NCAPs, are essential for their interaction. Detailed molecular analysis of a representative phloem NCAP, Cm-PP16-1, identified the specific residues on which glycosylation and phosphorylation must occur for effective binding to NCAPP1. Microinjection studies confirmed that posttranslational modification on these residues is essential for cell-to-cell movement of Cm-PP16-1. Lastly, a glutathione S-transferase (GST)-Cm-PP16-1 fusion protein system was employed to test whether the peptide region spanning these residues was required for cell-to-cell movement. These studies established that a 36-amino acid peptide was sufficient to impart cell-to-cell movement capacity to GST, a normally cell-autonomous protein. These findings are consistent with the hypothesis that a phosphorylation-glycosylation recognition motif functions to control the binding of a specific subset of phloem NCAPs to NCAPP1 and their subsequent transport through plasmodesmata.
Links	PubMed PMC1955715 Online version:10.1105/tpc.107.052522
Keywords	Amino Acid Motifs; Amino Acid Sequence; Biological Transport; Cucurbita/cytology; Cucurbita/metabolism; Glycosylation; Immunoprecipitation; Molecular Sequence Data; Mutation/genetics; Peptides/chemistry; Phloem/cytology; Phloem/metabolism; Phosphorylation; Plant Proteins/chemistry; Plant Proteins/metabolism; Plasmodesmata/metabolism; Protein Binding; Protein Processing, Post-Translational; Protein Transport; Recombinant Proteins/metabolism; Serine/metabolism; Tobacco/metabolism; Tyrosine/metabolism
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