Lobe IB of the ATPase domain of Kar2p/BiP interacts with Ire1p to negatively regulate the unfolded protein response in Saccharomyces cerevisiae.

The endoplasmic reticulum HSP70 chaperone BiP/Kar2p is both the sensor for the unfolded protein response (UPR) in the yeast Saccharomyces cerevisiae and a target of transcriptional up-regulation by this signaling pathway. In this study, the molecular form of Kar2p that interacts with the Ire1p transmembrane receptor kinase to inhibit UPR signaling was shown to be the substrate-free, ATP-bound conformation. Oligosaccharide shielding experiments localized the binding site for Ire1p to the top of the back face of lobe IB of the Kar2p ATPase domain.

Obscurin is a ligand for small ankyrin 1 in skeletal muscle.

The factors that organize the internal membranes of cells are still poorly understood. We have been addressing this question using striated muscle cells, which have regular arrays of membranes that associate with the contractile apparatus in stereotypic patterns. Here we examine links between contractile structures and the sarcoplasmic reticulum (SR) established by small ankyrin 1 (sAnk1), a approximately 17.