Adapter protein implicated in the regulation of a large spectrum of both general and specialized signaling pathways. Binds to a large number of partners, usually by recognition of a phosphoserine or phosphothreonine motif. Binding generally results in the modulation of the activity of the binding partner (By similarity). Binds with varying affinity to various synthetic phosphopeptides having a consensus binding motif RSX(pS/pT)XP, called mode-1, where X is any residue and pS/pT is a phosphorylated serine/threonine, and to synthetic phosphopeptides having a consensus binding motif Xp(S/T)X1-2-COOH, called mode-3, in which the phosphorylated residue occupies the penultimate C-terminal position in the target protein, but does not bind to their unphosphorylated counterparts (PubMed:19733174). Binds to synthetic human RAF1 phosphopeptides, but not to their unphosphorylated forms. Binds to difopein, a polypeptide containing a phosphorylation-independent binding motif (PubMed:16368691, PubMed:19733174). Involved in encystation (PubMed:19733174). Involved in cell proliferation. Required for actin and tubulin cytoskeletal organization. Regulates actin filament formation and nuclear size (PubMed:28932813). Homodimer (PubMed:16368691, PubMed:24658679, PubMed:28932813, PubMed:26551337, PubMed:22452640). Homodimerizes via N-terminal domains (PubMed:24658679, PubMed:26551337). Oligomerizes forming homotrimers, homotetramers and protein filaments. Oligomerization is hindered by polyglycylation in vivo (PubMed:24658679). Interacts with a large number of both cytosolic and membrane proteins in trophozoites and encysting parasites (PubMed:16368691, PubMed:22452640). Interacts with a serine/threonine protein kinase GL50803_112076 (gCDC7). Component of a multiprotein complex containing gCDC7 and GL50803_94117 (gDBF4), a regulatory subunit of gCDC7, during both the trophozoite and encysting stages of the parasite. Interacts with fructose-bisphosphate aldolase GL50803_11043 (gFBA), pyruvate kinase GL50803_17143 (gPyk), acetyl-CoA synthetase GL50803_13608 (gACS), protein kinase GL50803_22165 (gSTE), DEAD box RNA helicase GL50803_34684 (gVASA) and Golgi/cell cycle associated protein GL50803_17472 (gGCCA) (PubMed:22452640). Interacts with actin (PubMed:24728194, PubMed:28932813). Interacts with both monomeric phosphorylated and unphosphorylated actin. The interaction is enhanced by phosphorylation of actin and inhibited by Rho GTPase Rac (PubMed:28932813). In trophozoites and cysts, localizes intensely in the cytoplasm. Not detected in the central area of the cell corresponding to the median body nor in flagella. Detected in the nuclei of the encysting cells. Nuclear localization increases during the transition of cells from the early to the late encysting stage. Does not localize to the encystation-specific vesicles of the encysting cells (PubMed:16368691, PubMed:19733174). In interphase cells, detected throughout the cell with somewhat enriched at the cortex and perinuclear region. Associates with the intracytoplasmic axonemes of all flagella, but it is most apparent in the anterior flagella of interphase cells. Localizes also to the nuclear envelope/endoplasmic reticulum and to the microtubule bare area of the ventral disc during interphase. In mitotic cells, disassociates from the intracytoplasmic axonemes and localizes around the spindle. During cytokinesis, localizes with the ingressing furrow, which does not utilize a contractile ring (PubMed:28932813). Does no colocalize with F-actin (PubMed:24728194, PubMed:28932813). Expressed during excystation, the differentiation from cyst to trophozoite (at protein level) (PubMed:19861170). Expressed in trophozoites (at protein level) (PubMed:24658679, PubMed:19733174, PubMed:24147113, PubMed:24728194, PubMed:28932813, PubMed:22452640, PubMed:23058231, PubMed:21135098). Highly expressed during encystation stage, the differentiation from trophozoite to cyst (at protein level) (PubMed:24658679, PubMed:19733174, PubMed:24147113, PubMed:22452640). Expressed in feces extracted cysts (at protein level) (PubMed:19861170, PubMed:23058231). Expression in them is significantly lower than in trophozoites (at protein level) (PubMed:23058231). Constitutively expressed throughout the life cycle (PubMed:16368691). By encystation. Phosphorylated constitutively throughout the life cycle. Phosphorylation is very high in trophozoites and encysting cells of 12 hours (PubMed:16368691). Phosphorylated during excystation (PubMed:19861170). Phosphorylation promotes its binding to various target proteins and is critical for encystation process. Phosphorylation modification is not influenced by polyglycylation modification (PubMed:19733174). Polyglycylated on a glutamate residue, resulting in polyglycine chain on the gamma-carboxyl group (PubMed:16368691, PubMed:24658679, PubMed:19733174, PubMed:24147113, PubMed:21135098). Polyglycylated by the tubulin--tyrosine ligase-like protein GL50803_8456 (gTTLL3). The polyglycine chain is shortened by metallopeptidases of the M20 family, namely dipeptidases GL50803_15832 (gDIP1) and GL50803_8407 (gDIP2) (PubMed:21135098). The length of the polyglycine chain is developmental stage-dependent. In trophozoites, glycine residues range from 10 to 31, with the greatest occurrence of 21 residues. In 12 hour encystation stage, glycine residues range from 6 to 22, with the greatest occurrence of 10 residues. The differential rate of polyglycylation/deglycylation during the encystation process regulates the intracellular localization of this protein. Relocalizes partially from the cytoplasm inside the nuclei following the shortening of the polyglycine chain in encysting cells (PubMed:16368691, PubMed:19733174). Polyglycylation modification is not influenced by phosphorylation modification (PubMed:19733174). Polyglycylation prevents oligomerization in vivo (PubMed:24658679). Knockdown with morpholino results in dramatically reduced parasite growth, accumulation of multinucleate cells, abnormal flagellar positioning, and polarity and cytokinesis defects. Overall cytoplasmic actin organization is disrupted with ectopic short actin filaments, however, nuclei are enlarged with actin filaments covering the width of the nuclei. This protein may be used to design small molecules that inhibit its interactions with the target proteins. The inhibitors could be used as drugs to treat giardiasis, a disease caused by this parasite. Despite sequential and structural similarity, is not a functional ortholog of Drosophila 14-3-3 protein epsilon. Belongs to the 14-3-3 family.