Membrane chaperone Shr3 assists in folding amino acid permeases preventing precocious ERAD.

The yeast endoplasmic reticulum (ER) membrane-localized chaperone Shr3 plays a critical role in enabling amino acid permeases (AAPs) to fold and attain proper structures required for functional expression at the plasma membrane. In the absence of Shr3, AAPs specifically accumulate in the ER, where despite the correct insertion of their 12 transmembrane segments (TMSs), they aggregate forming large molecular weight complexes. We show that Shr3 prevents aggregation and facilitates the functional assembly of independently coexpressed N- and C-terminal fragments of the general AAP Gap1.

Three-dimensional imaging of in situ specimens with low-dose electron tomography to analyze protein conformation.

We describe a novel three-dimensional (3-D) imaging tool for analysis of protein conformation of in situ samples. Sidec (Sidec Technologies AB, Stockholm, Sweden) electron tomography (SET) uses low-dose electron tomography and a refinement algorithm to reconstruct individual proteins and macromolecular complexes. The approach has successfully reconstructed therapeutic proteins in solution.