In cooperation with pkc-3, required for establishing cell polarity and regulating spindle orientation in the early embryo (PubMed:8521491, PubMed:9716526). Localization is crucial for recruiting par-6 and pkc-3 to the peripheral apical cortex and restricting par-2 to basolateral surfaces (PubMed:8898226, PubMed:9834192). Necessary for apicobasal and anterior-posterior asymmetries associated with cell adhesion and gastrulation during the first few cycles of embryogenesis, and also for epithelial cell polarity in the distal spermatheca (PubMed:13129846, PubMed:15151982). Regulates the asymmetric localization of csnk-1, ppk-1 and gpr-1/2 during the first embryonic division (PubMed:14534135, PubMed:18694560). Required, together with pkc-3, for the localization of par-6; par-6 is involved in localizing/maintaining par-3 at the cell periphery. Interacts with par-6 and pkc-3 for localization at the periphery of anterior cortex of the embryo. Cytoplasmic and cell periphery. Asymmetrically distributed at the periphery of the zygote and in dividing blastomeres of the germline lineage. Coexpressed with par-6; patchy expression observed at the periphery after completion of meiosis I and in meiosis II. On completion of metaphase II, expression is restricted to the anterior 85% of embryo length; this decreases to 55% in embryos between prophase and telophase of the first mitosis. During the first cleavage, expression is detected in the advancing furrow. Transiently coexpressed and colocalized asymmetrically with par-6 and pkc-3, in the developing somatic gonad, including the spermathecal precursor cells of L4 larvae. Expressed both maternally and zygotically. Belongs to the PAR3 family.