Regulation of plasma membrane protein abundance controls responses to changing environmental conditions. Membrane proteins destined for degradation are marked by ubiquitin, endocytosed and subsequently transferred by the ESCRT (Endosomal Sorting Complex required for Transport) machinery to the final degradation compartment. The ESCRT machinery, consisting of four complexes, is highly conserved with the exception of the ESCRT-0, which as such is not found in plants. Yet, first contact with ubiquitinated cargo is initiated by the ubiquitin binding domain (UBD) of the ESCRT-0 complex. Thus the discovery of a family of nine proteins, called TOLs (Tom1 like), as potential ESCRT-0 orthologs in Arabidopsis thaliana gave a new perspective to plant endosomal trafficking. As mammalian and yeast ESCRT-0 subunits share similar UBDs with the TOLs, related functionality was assumed. In order to characterize the unique TOL proteins, I mutated the highly conserved amino acids reported to be important for ubiquitin binding. With these mutated constructs, I performed in vitro binding studies and could successfully show a substantial decrease in ubiquitin binding. I used these constructs to design in vivo TOL constructs to analyze the effect of the lack of ubiquitin binding in planta. Initial analysis of these plant lines showed that the mutation of the UBDs not only affects the binding to ubiquitin but also the localization of the TOL proteins. These results not only verify the importance of these UBDs of the TOL proteins but further suggest their interplay in the regulation of the function of the proteins and potentially the entire machinery that is responsible for the degradation of plasma membrane localized proteins. Further analysis will be needed to confirm these results. Nevertheless, this study serves as a solid corner stone to unravel the interplay between ubiquitinated plasma membrane proteins destined for degradation and the endosomal sorting machinery.