Matters arising: Forced Symmetry Artifacts in a Prohibitin Complex Structure

Abstract

In a recent publication, Lange et al.1 proposed an 11-spoked wheel model for the mitochondrial prohibitin complex consisting of six PHB1 and five PHB2 subunits built into low resolution density obtained from 11-fold symmetry averaging. The proposed unequal stoichiometry is inherently incompatible with symmetry. The building of an asymmetric molecular model into density obtained by 11-fold symmetry averaging is inherently self-contradictory. This contradiction alone calls the validity of the derived structure into question. Our own data revealed that the complex primarily adopts an asymmetric open conformation in situ. We show that it was the incorrect symmetry imposition on the open conformation that led to the spoked wheel density reported by Lange et al.. Further validation by re-analysis of crosslinking-mass spectrometry data, and a test of in situ template matching all support a larger prohibitin complex architecture. These findings underscore the need for great care in the imposition of symmetry cryo-ET at less than atomistic resolution.