Plays a role in starvation-induced autophagy. Involved in mitophagy. Functions with ATG17 and ATG29 at the preautophagosomal structure (PAS) in order to form normal autophagosomes under starvation conditions. May be involved in microtubule function, such as chromosome segregation and karyogamy. Forms a stable complex with ATG17 and ATG29. Interacts directly with ATG29. The ATG17-ATG29-ATG31 complex interacts with the ATG1-ATG13 complex. Note=The interaction with the ATG1-ATG13 complex is induced by starvation. Phosphorylated. Present with 486 molecules/cell in log phase SD medium.