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PA_VSR: Protease-associated (PA) domain-containing plant vacuolar sorting receptor (VSR). This group includes various PA domain-containing VSRs such as garden pea BP-80, pumpkin PV72, and various Arabidopsis VSRs including AtVSR1. In contrast to most eukaryotes, which only have one or two VSRs, plants have several. This may in part be a reflection of having a more complex vacuolar system with both lytic vacuoles and storage vacuoles. The lytic vacuole is thought to be equivalent to the mammalian lysosome and the yeast vacuole. Pea BP-80 is a type 1 transmembrane protein, involved in the targeting of proteins to the lytic vacuole; it has been suggested that this protein also mediates targeting to the storage vacuole. PV72 and AtVSR1 may mediate transport of seed storage proteins to protein storage vacuoles. The significance of the PA domain to VSRs has not been ascertained. It may be a protein-protein interaction domain. At peptidase active sites, the PA domain may participate in substrate binding and/or promoting conformational changes, which influence the stability and accessibility of the site to substrate.
Jiyao W et al.(2023). "The conserved domain database in 2023.",