Lipid transfer protein required for autophagosome completion and peroxisome degradation. Tethers the edge of the isolation membrane (IM) to the endoplasmic reticulum (ER) and mediates direct lipid transfer from ER to IM for IM expansion. ATG2 binds to the ER exit site (ERES), which is the membrane source for autophagosome formation, using basic residues in its N-terminal region (NR) and to the expanding edge of the IM through its C-terminal region. The latter binding is assisted by an ATG18-PtdIns3P interaction. ATG2 then extracts phospholipids from the membrane source using its NR and transfers them to ATG9 to the IM through its predicted beta-sheet-rich structure for membrane expansion. a 1,2-diacyl-sn-glycero-3-phosphocholine(in) = a 1,2-diacyl-sn-glycero-3-phosphocholine(out) a 1,2-diacyl-sn-glycero-3-phospho-L-serine(in) = a 1,2-diacyl-sn-glycero-3-phospho-L-serine(out) a 1,2-diacyl-sn-glycero-3-phosphoethanolamine(in) = a 1,2-diacyl-sn-glycero-3-phosphoethanolamine(out) Still forms preautophagosomal structures (PAS) in proximity to the vacuolar membrane (PubMed:26442587). Kluyveromyces marxianus proteins are shorter in length and have a more ordered secondary structure than their S.cerevisiae counterparts, which might contribute to the superior thermotolerance and solubility (PubMed:26442587). K.marxianus could be therefore useful as a new model organism for further elucidation of the molecular details of autophagy (PubMed:26442587). Belongs to the ATG2 family.