nsLTPs

nsLTPs, or non-specific lipid-transfer proteins, are a family of small, secreted plant proteins involved in lipid binding and transfer. They are typically 7–10 kDa in maturity, and are rich in conserved cysteine residues, usually arranged as eight cysteines that form four disulfide bonds to stabilize a compact, highly stable fold. Most nsLTPs carry an N-terminal signal peptide that directs them into the secretory pathway and into the apoplast, where they function outside the plasma membrane.

The nsLTP family is commonly divided into two major subfamilies, LTP1 and LTP2, which differ in size and sequence. LTP1 members are about 9 kDa, whereas LTP2 members are around 7 kDa. Both types are encoded by large multigene families and are widespread among seed plants, particularly angiosperms. Some nsLTPs also function as pollen allergens.

Functionally, nsLTPs can bind and transfer a variety of lipids, including phospholipids and fatty acids, and they are implicated in lipid trafficking between membranes and in the deposition of lipids in the plant cuticle and pollen coat. In addition to their roles in development and barrier formation, many nsLTPs participate in plant defense, with antimicrobial activity observed in some members and expression induced by pathogen attack and by defense-related hormones such as jasmonic acid, salicylic acid, and abscisic acid.

Localization is primarily extracellular (apoplastic), consistent with their secretion and involvement in cell-wall-associated processes. Due to their abundance and sometimes allergenic properties, nsLTPs are frequently studied as models of lipid transfer and as markers of stress responses in plants.