Structure of the Hsp110:Hsc70 nucleotide exchange machine.

Hsp70s mediate protein folding, translocation, and macromolecular complex remodeling reactions. Their activities are regulated by proteins that exchange ADP for ATP from the nucleotide-binding domain (NBD) of the Hsp70. These nucleotide exchange factors (NEFs) include the Hsp110s, which are themselves members of the Hsp70 family. We report the structure of an Hsp110:Hsc70 nucleotide exchange complex. The complex is characterized by extensive protein:protein interactions and symmetric bridging interactions between the nucleotides bound in each partner protein\u27s NBD. An electropositive pore allows nucleotides to enter and exit the complex. The role of nucleotides in complex formation and dissociation, and the effects of the protein:protein interactions on nucleotide exchange, can be understood in terms of the coupled effects of the nucleotides and protein:protein interactions on the open-closed isomerization of the NBDs. The symmetrical interactions in the complex may model other Hsp70 family heterodimers in which two Hsp70s reciprocally act as NEFs

Quaternary structure independent folding of voltage-gated ion channel pore domain subunits

Every voltage-gated ion channel (VGIC) has a pore domain (PD) made from four subunits, each comprising an antiparallel transmembrane helix pair bridged by a loop. The extent to which PD subunit structure requires quaternary interactions is unclear. Here, we present crystal structures of a set of bacterial voltage-gated sodium channel (BacNaV) 'pore only' proteins that reveal a surprising collection of non-canonical quaternary arrangements in which the PD tertiary structure is maintained. This context-independent structural robustness, supported by molecular dynamics simulations, indicates that VGIC-PD tertiary structure is independent of quaternary interactions. This fold occurs throughout the VGIC superfamily and in diverse transmembrane and soluble proteins. Strikingly, characterization of PD subunit-binding Fabs indicates that non-canonical quaternary PD conformations can occur in full-length VGICs. Together, our data demonstrate that the VGIC-PD is an autonomously folded unit. This property has implications for VGIC biogenesis, understanding functional states, de novo channel design, and VGIC structural origins

Comparison of 6q25 Breast Cancer Hits from Asian and European Genome Wide Association Studies in the Breast Cancer Association Consortium (BCAC)

Peer reviewe

Crystal Structure of the RNA Lariat Debranching Enzyme Dbr1 with Hydrolyzed Phosphorothioate RNA Product

The RNA lariat debranching enzyme is the sole enzyme responsible for hydrolyzing the 2′-5′ phosphodiester bond in RNA lariats produced by the spliceosome. Here, we test the ability of Dbr1 to hydrolyze branched RNAs (bRNAs) that contain a 2′-5′-phosphorothioate linkage, a modification commonly used to resist degradation. We attempted to cocrystallize a phosphorothioate-branched RNA (PS-bRNA) with wild-type Entamoeba histolytica Dbr1 (EhDbr1) but observed in-crystal hydrolysis of the phosphorothioate bond. The crystal structure revealed EhDbr1 in a product-bound state, with the hydrolyzed 2′-5′ fragment of the PS-bRNA mimicking the binding mode of the native bRNA substrate. These findings suggest that product inhibition may contribute to the kinetic mechanism of Dbr1. We show that Dbr1 enzymes cleave phosphorothioate linkages at rates ∼10,000-fold more slowly than native phosphate linkages. This new product-bound crystal structure offers atomic details, which can aid inhibitor design. Dbr1 inhibitors could be therapeutic or investigative compounds for human diseases such as human immunodeficiency virus (HIV), amyotrophic lateral sclerosis (ALS), cancer, and viral encephalitis