Concerns with yeast mitochondrial ADP/ATP carrier's integrity in DPC.

Abstract

Hereby, we wish to note our objections to a paper called “Substrate-modulated ADP/ATP-transporter dynamics revealed by NMR relaxation dispersion” by Brüschweiler et al., published in NSMB in 20151. The subject is the yeast mitochondrial ADP/ATP carrier AAC3, which we have studied in great detail ourselves. In particular, we have solved its structure by electron and x-ray crystallography and have studied its interactions with the specific inhibitors atractyloside (ATR) and carboxyatractyloside (CATR) by single-molecule force spectroscopy4. In this paper, the authors claim that AAC3 can be refolded to homogeneity from inclusion bodies produced in Escherichia coli by using the detergent dodecyl-phosphocholine (DPC), better known as Foscholine-12 (Anatrace), and that AAC3 is maintained in a folded and active state for the duration of isothermal titration calorimetry (ITC) and NMR experiments. However, in our hands the presence of DPC leads to immediate loss of tertiary structure and inactivation of AAC3 when isolated from the inner membrane of mitochondria, where it was folded and active as shown by functional complementation.