Structure of the human BBSome core complex in the open conformation

Abstract

The BBSome is a heterooctameric protein complex that plays a central role in primary cilia homeostasis. Its malfunction causes the severe ciliopathy Bardet-Biedl syndrome (BBS). The complex acts as a cargo adapter that recognizes signaling proteins such as GPCRs and links them to the intraflagellar transport machinery. The underlying mechanism is poorly understood.Here we present a high-resolution cryo-EM structure of a human heterohexameric core subcomplex of the BBSome. The structure reveals the architecture of the complex in atomic detail. It explains how the subunits interact with each other and how disease-causing mutations hamper this interaction. The complex adopts a conformation that is open for binding to membrane-associated GTPase Arl6 and a large positively charged patch likely strengthens the interaction with the membrane. A prominent negatively charged cleft at the center of the complex is likely involved in binding of positively charged signaling sequences of cargo proteins.

TRPV channel OCR-2 is distributed alongC. eleganschemosensory cilia by diffusion in a local interplay with intraflagellar transport

“…The interaction of OCR-2 and other TPs to IFT trains has been shown to be mediated by the BBSome protein complex, which is essential for chemotaxis (Blacque et al, 2004). Recent cryo-EM studies of the BBSome have revealed molecular details of this interaction, a negatively charged cleft on the BBSome surface that is likely involved in the binding of cargo proteins (Klink et al, 2019). In another study it has been suggested that the GTPase ARL6/BBS-3 is activated when it interacts specifically with the BBSome, allowing for the connection between IFT-trains and transmembrane cargoes (Chou et al, 2019).…”

The evolution of SPHIRE-crYOLO particle picking and its application in automated cryo-EM processing workflows

“…crYOLO [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] . For example, Pang et al 23 used crYOLO to selectively pick particles, which were attached to liposomes; Rogala et al 14 highlighted in their study about mTORC1 that crYOLO was especially useful to exclude particles on carbon; Joppe et al 24 made use of crYOLO in a streamlined pipeline for rapid structure determination of yeast fatty acid synthase; and the new filament mode was recently used by Pospich et al to examine the structural effects of toxins on actin filaments 16 .…”