Lethal giant larvae 1 (LGL-1) binds to negatively charged phospholipids through specific basic residues of a membrane binding sequence. LGL-1 membrane binding induces the formation of an alpha-helix in the membrane binding sequence. Reconstitution of LGL-1 phosphorylation in giant unilamellar vesicles by atypical protein kinase C LGL-1 residues required for membrane binding are required for localization and cell polarity in vivo.