Autophagy factor required for autophagosome formation and mitophagy. Target of the TOR kinase signaling pathway that regulates autophagy through the control of the phosphorylation status of ATG13 and ULK1, and the regulation of the ATG13-ULK1-RB1CC1 complex. Through its regulation of ULK1 activity, plays a role in the regulation of the kinase activity of mTORC1 and cell proliferation. Part of a complex consisting of ATG13, ULK1 and RB1CC1. Interacts with ATG101. Interacts with ULK1 (via C-terminus). Interacts with ULK2 (via C-terminus). Interacts (via the LIR motif) with GABARAP, GABARAPL, GABARAPL2. Interacts (via the LIR motif) with MAP1LC3A, MAP1LC3B and MAP1LC3C. Interacts with TAB2 and TAB3. Interacts with C9orf72. Under starvation conditions, is localized to puncate structures primarily representing the isolation membrane; the isolation membrane sequesters a portion of the cytoplasm resulting in autophagosome formation. The LIR motif (LC3-interacting region) is required for the interaction with the ATG8 family proteins GABARAP, GABARAPL, GABARAPL2, and MAP1LC3A. Phosphorylated by ULK1, ULK2 and mTOR. Phosphorylation status depends on nutrient-rich conditions; dephosphorylated during starvation or following treatment with rapamycin. ULK1-mediated phosphorylation of ATG13 at Ser-318 is required for efficient clearance of depolarized mitochondria. Belongs to the ATG13 family. Metazoan subfamily.