5jm9 | pdb_00005jm9
Structure of S. cerevesiae mApe1 dodecamer
Structural highlights
Function[AMPL_YEAST] Resident vacuolar enzyme that catalyzes the removal of amino acids from the N-terminus of peptides and proteins. Also acts as the major cargo protein of the cytoplasm-to-vacuole targeting (Cvt) pathway. The precursor form of aminopeptidase 1 (prApe1) assembles into dodecamers and the propeptide mediates the aggregation of dodecamers into higher multimers. The multimers are then recognized via the propeptide by their receptor ATG19, and ATG19 further interacts with ATG11, which tethers the APE1-ATG19 complex to the pre-autophagosomal structure (PAS). The cargo-receptor complex (also Cvt complex) is selectively enwrapped by a double-membrane structure termed the Cvt vesicle under vegetative growth conditions and by a similar but larger double-membrane structure termed the autophagosome under nitrogen starvation conditions. The Cvt vesicle or the autophagosome fuses with the vacuolar membrane and release its content in the vacuolar lumen. In the vacuole, prApe1 is processed into mature aminopeptidase 1 (mApe1).[1] [2] [3] [4] [5] [6] [7] [8] Publication Abstract from PubMedSelective autophagy is the mechanism by which large cargos are specifically sequestered for degradation. The structural details of cargo and receptor assembly giving rise to autophagic vesicles remain to be elucidated. We utilize the yeast cytoplasm-to-vacuole targeting (Cvt) pathway, a prototype of selective autophagy, together with a multi-scale analysis approach to study the molecular structure of Cvt vesicles. We report the oligomeric nature of the major Cvt cargo Ape1 with a combined 2.8 A X-ray and negative stain EM structure, as well as the secondary cargo Ams1 with a 6.3 A cryo-EM structure. We show that the major dodecameric cargo prApe1 exhibits a tendency to form higher-order chain structures that are broken upon interaction with the receptor Atg19 in vitro The stoichiometry of these cargo-receptor complexes is key to maintaining the size of the Cvt aggregate in vivo Using correlative light and electron microscopy, we further visualize key stages of Cvt vesicle biogenesis. Our findings suggest that Atg19 interaction limits Ape1 aggregate size while serving as a vehicle for vacuolar delivery of tetrameric Ams1. Higher-order assemblies of oligomeric cargo receptor complexes form the membrane scaffold of the Cvt vesicle.,Bertipaglia C, Schneider S, Jakobi AJ, Tarafder AK, Bykov YS, Picco A, Kukulski W, Kosinski J, Hagen WJ, Ravichandran AC, Wilmanns M, Kaksonen M, Briggs JA, Sachse C EMBO Rep. 2016 Jun 6. pii: e201541960. PMID:27266708[9] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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