RNA-binding protein involved in translational regulation and required for long-term memory (PubMed:28525754, PubMed:29105522). Required in mushroom body gamma neurons for long-term memory in male courtship (PubMed:17965711, PubMed:23083740). Binds to mRNA 3'-UTRs (PubMed:20547833, PubMed:26638074, PubMed:24830287, PubMed:26095367, PubMed:32165583). In its monomeric form, acts as a translational repressor of genes involved in neuronal growth, synapse formation and protein turnover (PubMed:20547833, PubMed:26638074, PubMed:32165583). In its amyloid-like oligomeric form, acts as a translational activator (PubMed:26638074, PubMed:32165583). The monomeric form reduces poly(A) tail length and destabilizes mRNA while the oligomeric form protects and elongates the poly(A) tail and stabilizes mRNA (PubMed:26638074). Involved in asymmetric cell division in the central nervous system (PubMed:21900268). Plays a role in synapse formation and morphology at neuromuscular junctions by modulating the translation of the tumor suppressor brat (PubMed:29105522). Required for the progression of spermatogenesis through meiosis and for sperm differentiation (PubMed:23209437). During sperm differentiation, required to asymmetrically localize and activate the translation of protein kinase aPKC mRNAs which is necessary for spermatid cyst polarization (PubMed:24830287). Also required during spermatid cyst polarization for localization and translation of its own mRNA (PubMed:24830287). Required for initial memory acquisition (PubMed:26095367, PubMed:28525754). Following subsequent late dopaminergic pathway activation, recruits isoform B into a complex to activate translation of CaMKII which is required for long-term memory consolidation (PubMed:26095367). Monomer (PubMed:22284910, PubMed:23083740, PubMed:32165583). Upon neuronal stimulation, forms stable amyloid-like oligomers composed of isoform A and isoform B which are required for formation of persistent long-term memory (PubMed:22284910, PubMed:23083740, PubMed:32165583). Isoform A is critical for oligomer formation (PubMed:22284910, PubMed:23083740). Phe-5 of isoform A is required for amyloid-like oligomerization (PubMed:22284910, PubMed:26812143). Rapidly forms amyloids and toxic intermediates are extremely transient (PubMed:26812143). Unlike in the adult nervous system, remains monomeric in the early embryo (PubMed:32165583). Interacts with the translational regulator bol (PubMed:23209437). Interacts with Tob; the interaction is enhanced by neuronal stimulation, stabilizes isoform A and induces oligomerization (PubMed:24523662). In embryonic and larval nervous system, concentrated in the perikaryon (PubMed:21900268). In the adult central nervous system, localizes to synaptic terminals (PubMed:21900268). In the ovary, localizes to the cytoplasm of nurse cells (PubMed:21900268). Localizes to neuromuscular junctions (PubMed:29105522). In spermatocytes, localizes throughout the cytoplasm with higher levels concentrated in a ring around the nucleus (PubMed:23209437). The oligomeric form is enriched in the synaptic region (PubMed:22284910). Broadly expressed throughout the nervous system of embryo, larva and adult including the ventral nerve cord and brain (at protein level) (PubMed:23083740, PubMed:32165583). In early embryos, deposited maternally and distributed uniformly throughout the embryo until the extended germband stage (PubMed:21900268). By mid-embryogenesis, highest levels are found in the central and peripheral nervous systems with lower expression also detected in the ectoderm and mesoderm (PubMed:21900268). In adults, high levels are present in the head and body of both sexes with higher expression in testis than ovary (PubMed:21900268). In the ovary, expressed in both germ and follicle cells (PubMed:21900268). In adult head, predominantly neuronal with broad expression throughout the brain and ventral ganglia including the mushroom body (PubMed:17965711, PubMed:21900268). Expressed in 0- to 2-hour-old embryos (at protein level) (PubMed:32165583). Expressed in the larval motor neuron cells in the brain (at protein level) (PubMed:29105522). Expressed throughout development in both the soma and germline. Widely expressed in early embryos with levels dropping during mid-embryogenesis and increasing again in late embryogenesis. Expression is relatively low during larval stages with lowest levels in the first and second instars and an increase during the third instar. Levels increase substantially during the pupal stage and remain relatively high in the adult. In the ovary, little expression in the germarium or previtellogenic stage chambers with levels increasing midway through oogenesis and remaining high until stage 10 (PubMed:21900268). In the testis, there is substantial up-regulation after mitosis is finished and the interconnected spermatocytes begin to grow (PubMed:23209437). Expression peaks as the mature spermatocytes go through meiosis and high levels are found in 32- and 64-cell spermatid cysts with expression persisting after the spermatids in the 64-cell cysts start differentiation and disappearing once elongation and nuclear condensation are completed (PubMed:23209437). In the adult brain the mRNA is expressed as an unspliced non-protein coding mRNA; inclusion of isoform A-specific exon in the mature transcript is important for long-term memory; mRNA levels depends on behavioral stimulus and splicing depends on the activity of the splicing regulator ps. The RNA-binding region is not essential for long-term memory. The RNA-binding region is essential for long-term memory. The N-terminal Gln/His-rich domain is necessary and sufficient for long-term memory and is required for formation of amyloid-like oligomers with isoform B (PubMed:17965711, PubMed:23083740). Binds transition metals (PubMed:28763009). Might bind lipid membranes (PubMed:28700922). The N-terminal Gln/His-rich domain is both dispensable and insufficient for long-term memory and for formation of amyloid-like oligomers with isoform A. Phosphorylation regulates interaction with Tob and oligomerization. Protein phosphatase 2A keeps both Orb2 and Tob in an unphosphorylated form. Following synaptic activation, unphosphorylated Orb2 is bound and stabilized by unphosphorylated Tob. Tob recruits activated LimK which phosphorylates both Orb2 and Tob and enhances Orb2 oligomerization. Substantially reduced viability with surviving males being completely sterile due to a failure of spermatocytes to complete meiosis with arrest happening at the G2-M transition (PubMed:23209437). Defective spermatid cyst polarization (PubMed:24830287). RNAi-mediated knockdown in motor neurons decreases number of synapses and accumulation of the tumor suppressor brat at neuromuscular junctions (NMJ) (PubMed:29105522). Simultaneous knockdown of the tumor suppressor brat restablishes the number of synapses at NMJ (PubMed:29105522). Fails to form stable long-term memory during male courtship suppression, in which a male fly, upon repeated exposure to an unreceptive female, suppresses its courting behavior for days (PubMed:28525754). In neurons, increases levels of the tumor suppressor brat (PubMed:29105522). Lowering pH destabilizes the protein filaments. Wrong choice of frame.