Protein: Protein PTST, chloroplastic (PROTEIN TARGETING TO STARCH) (Q94AX2)
Organism: Arabidopsis thaliana (Mouse-ear cress)
Function: Involved in targeting GBSS1 to the starch granule. Was originally thought to be a carbohydrate-binding scaffold protein, but it has been shown that it is mainly found as a soluble protein and that interaction with GBSS1 is a pre-requisite for subsequent starch granule binding. Dissociation from starch as a function of pH, Mg(2+) concentration or redox state is not observed. Interacts primarily with amylopectin and is required for amylose synthesis.
Subcellular location: Plastid, chloroplast stroma {ECO:0000269|PubMed:19038037, ECO:0000269|PubMed:25710501}. Note=The vast majority of PTST is soluble and only a small amount is granule-bound. No localization to the starch granules in the absence of GBSS1. {ECO:0000269|PubMed:25710501}.
Sequence: MGCVPRIEFGCSSQSLTLSWNLRAWNLCRLNTISHFQKLPYPLVASTRKHYKNSLLLKRFLVGVGTEESSLSEDLLDESLSRPLTSDELKSLLIDTERSKLVKKLSEANQQNRFLKRQLKTQEHEITNIKTELALMELEVQALVKLAEEIANLGIPQGSRKISGKYIQSHLLSRLDAVQKKMKEQIKGVEAAQSKEVHVFWIGMAESVQVMGSFDGWSQREDLSPEYSALFTKFSTTLFLRPGRYEMKFLVDGEWQISPEFPTSGEGLMENNVLVVE
InterPro domains: - IPR014756: Immunoglobulin E-set (homologous_superfamily) [196-276]
- IPR032640: AMP-activated protein kinase, glycogen-binding domain (domain) [198-267]
- IPR013783: Immunoglobulin-like fold (homologous_superfamily) [188-277]
Interaction partners: - Granule-bound starch synthase 1, chloroplastic/amyloplastic
- MAR-binding filament-like protein 1
- Probable starch synthase 4, chloroplastic/amyloplastic
- Isoamylase 1, chloroplastic
- Phosphoglucan phosphatase DSP4, chloroplastic
- Isoamylase 2, chloroplastic
- Phosphoglucan phosphatase LSF2, chloroplastic
- 4-alpha-glucanotransferase DPE1, chloroplastic/amyloplastic
- Isoamylase 3, chloroplastic
- 1,4-alpha-glucan-branching enzyme 3, chloroplastic/amyloplastic
Gene Ontology annotations:
Molecular Function (MF): GO:0003674 (molecular function), GO:0005488 (binding), GO:0003824 (catalytic activity), GO:0030246 (carbohydrate binding), GO:0016740 (transferase activity), GO:0005515 (protein binding), GO:0030247 (polysaccharide binding), GO:0016757 (glycosyltransferase activity)
Biological Process (BP): GO:0008150 (biological process), GO:0008152 (metabolic process), GO:0009987 (cellular process), GO:0009058 (biosynthetic process), GO:0044237 (cellular metabolic process), GO:0071704 (organic substance metabolic process), GO:0044238 (primary metabolic process), GO:0044255 (cellular lipid metabolic process), GO:0044249 (cellular biosynthetic process), GO:0005975 (carbohydrate metabolic process), GO:1901576 (organic substance biosynthetic process), GO:0006629 (lipid metabolic process), GO:0044260 (cellular macromolecule metabolic process), GO:0043170 (macromolecule metabolic process), GO:0044262 (cellular carbohydrate metabolic process), GO:1901135 (carbohydrate derivative metabolic process), GO:0009059 (macromolecule biosynthetic process), GO:1903509 (liposaccharide metabolic process), GO:0034645 (cellular macromolecule biosynthetic process), GO:1901137 (carbohydrate derivative biosynthetic process), GO:0008610 (lipid biosynthetic process), GO:0008653 (lipopolysaccharide metabolic process), GO:0044264 (cellular polysaccharide metabolic process), GO:0016051 (carbohydrate biosynthetic process), GO:0005976 (polysaccharide metabolic process), GO:0034637 (cellular carbohydrate biosynthetic process), GO:0000271 (polysaccharide biosynthetic process), GO:0009103 (lipopolysaccharide biosynthetic process), GO:0033692 (cellular polysaccharide biosynthetic process), GO:0044042 (glucan metabolic process), GO:0006073 (cellular glucan metabolic process), GO:0009250 (glucan biosynthetic process), GO:0005982 (starch metabolic process), GO:0019252 (starch biosynthetic process)
Cellular Component (CC): GO:0005575 (cellular component), GO:0110165 (cellular anatomical entity), GO:0005622 (intracellular anatomical structure), GO:0043226 (organelle), GO:0005737 (cytoplasm), GO:0043229 (intracellular organelle), GO:0043227 (membrane-bounded organelle), GO:0009536 (plastid), GO:0009507 (chloroplast), GO:0043231 (intracellular membrane-bounded organelle)