The yeast cell model generated to identify the putative mitochondrial NAG transporter/s. Yeast cells lacking the ARG8 gene are auxotrophic for arginine. The expression of the E. coli argB-E in the cytosol makes cells dependent on the exit of NAG from the matrix. In this model, the expression of a functional unknown mitochondrial transporter able to catalyze the efflux of NAG from the matrix will make these cells able to grow in the absence of arginine. The part of the yeast mitochondrial arginine biosynthetic pathway not functional in the model is shaded brown whereas the newly created arginine biosynthetic pathway is shaded blue. argB, argC, argD and argE, E. coli NAG kinase, N-acetyl-glutamyl-5-phospate reductase, N-acetyl-ornithine aminotransferase and N-acetyl ornithine deacetylase, respectively; ARG2, NAG synthase; ARG5,6, N-acetylglutamate kinase and N-acetyl-5-glutamyl-phosphate reductase; ARG8, N-acetyl-ornithine aminotransferase; ARG7, N-acetyl-ornithine acetyltransferase; ARG11, mitochondrial ornithine transporter; ARG3, ornithine carbamoyl transferase; ARG1, argininosuccinate synthetase; ARG4, argininosuccinate lyase; NAGC??, putative mitochondrial NAG transporter.