Figure 1.

Schematic model depicting assembly of the Atg1 kinase complex. Atg17 first interacts with the Atg13-Vac8 proteins. Atg13 and Atg1 may be phosphorylated by Tor and/or PKA (Budovskaya et al., 2004; Schmelzle et al., 2004) or by downstream effectors. The highly phosphorylated form of Atg13 has a lower affinity for Atg1 (Kamada et al., 2000) and this form of the complex may promote the Cvt pathway. Partial dephosphorylation of Atg13 and Atg1 allows the assembly of the putative holo-complex that triggers autophagy. Atg17 is depicted as interacting with Atg1 via Atg13, but the interaction may be direct (see text). Factors that have previously been characterized as being relatively specific for the Cvt pathway are depicted in gray. The timing of assembly of the Atg11, Atg20, and Atg24 proteins is not known as denoted by dotted lines. See text for additional details.