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 (PubMed:26442587). 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 (By similarity). Plays particularly a role in pexophagy and nucleophagy (By similarity). With ATG13, is required for ATG1 activation by autophosphorylation (By similarity). Recruits ATG9 to the pre-autophagosomal structure (By similarity). Forms a complex with ATG13, ATG29 and CIS1/ATG31 (By similarity). The ATG17-ATG29-ATG31 complex interacts with the ATG1-ATG13 complex (By similarity). Forms a complex with SNX4 and ATG20 (By similarity). Interacts with ATG11 (By similarity). Mislocalizes ATG8 in the cytosol, when ATG11 is also deleted (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 ATG17 family.