Figure 2

Uptake of dipeptides by the ubr11 mutants. A host strain (ubr11∆ leu1 ura4) was transformed with ura4⁺ plasmids encoding Ubr11 mutant or wild type proteins. Their ability to rescue the growth defect of the leucine auxotrophic host strain in the presence of leucine-containing dipeptides was tested. Serially diluted cells were spotted on the medium containing the indicated peptides or leucine. The control medium lacked any source of leucine. The ubr11-T1 mutation, which impaired recognition of type 1 residues, did not affect the utilization of the dipeptides. In contrast, the type 2-specific ubr11-T2 mutant was mostly defective.