Generating symmetry in the asymmetric ABC transporter Pdr5 from Saccharomyces cerevisiae [Microbiology]

April 14th, 2014 by Gupta, R. P., Kueppers, P., Hanekop, N., Schmitt, L.

Pdr5 is a plasma membrane bound ABC transporter from Saccharomyces cerevisiae and involved in the phenomenon of resistance against xenobiotics, which is clinically relevant in bacteria, fungi and humans. Many fungal ABC transporters such as Pdr5 display an inherent asymmetry in their nucleotide-binding sites (NBS) unlike most of their human counterparts. This degeneracy of the NBSs is very intriguing and needs explanation in terms of structural and functional relevance. In this study we mutated non-consensus amino acid residues in the NBSs to its consensus counterpart and studied its effect on the function of the protein and effect on yeast cells. The completely &'re-generated&' Pdr5 protein was severely impaired in its function of ATP hydrolysis and of rhodamine 6G transport. Moreover, we observe alternate compensatory mechanisms to counteract drug toxicity in some of the mutants. In essence, we here describe the first attempts in restoring complete symmetry in an asymmetric ABC transporter and to study its effects, which might be relevant to the entire class of asymmetric ABC transporters.