Autophagy-specific protein that functions with ATG13, ATG29, and CIS1/ATG31 in response to autophagy-inducing signals as a scaffold to recruit other ATG proteins to organize pre-autophagosomal structure (PAS) formation. Modulates the timing and magnitude of the autophagy response, such as the size of the sequestering vesicles, through interacting with and regulating ATG1 kinase activity. Plays particularly a role in pexophagy and nucleophagy. With ATG13, is required for ATG1 activation by autophosphorylation of 'Thr-226'. Recruits ATG9 to the pre-autophagosomal structure. Also plays a role in regulation of filamentous growth (By similarity). Forms a complex with ATG13, ATG29 and CIS1/ATG31. The ATG17-ATG29-ATG31 complex interacts with the ATG1-ATG13 complex. Forms a complex with SNX4 and ATG20. Interacts with ATG11 and the conserved oligomeric Golgi (COG) complex subunits COG1, COG3 and COG4. Belongs to the ATG17 family.