The proline transport protein of Aspergillus nidulans is very similar to amino acid transporters of Saccharomyces cerevisiae.

In Aspergillus nidulans, the gene prnB encoding the major proline transport system is one of a cluster of four genes necessary and sufficient for the utilization of proline as sole nitrogen and/or carbon source. The prn cluster has been cloned and the sequence and transcript map of the prnB gene are presented in this paper. The predicted translated sequence consists of 570 amino acids, resulting in a molecular weight of 63,028 Daltons. Its hydropathy profile shows 10 hydrophobic segments typical of integral membrane proteins. No N-terminal hydrophobic signal peptide is present, the N-terminal and C-terminal ends of the protein being hydrophilic. Similar results were previously found for the arginine and histidine transporters of Saccharomyces cerevisiae, with which the prnB transporter shares regions of highly conserved amino acid sequences. Using S1 mapping and Northern blot analyses, we confirm the presence of a unique inducible prnB transcript of 1.9 kb.