STRUCTURAL STUDIES OF THE EXOMER COAT PROTEIN COMPLEX

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A full third of all gene products are thought to be shuttled through the secretory system of eukaryotic cells. There are numerous human diseases associated with defects in components of the secretory system, or with mutations that disrupt the ability of a protein to interface with the membrane trafficking machinery. Transport of protein ¿¿Scargo¿¿¿ between membrane-bound compartments is a tightly regulated process involving vesicular membrane carriers. A classical membrane vesicle is created via membrane deformation achieved in part by cytosolic ¿¿Scoat¿¿¿ proteins. Coat proteins not only shape membranes, but also play an important role in selecting cargo incorporated into transport carriers. Recent studies have established the existence of a new membrane coat complex responsible for trafficking select cargo from the trans-Golgi network (TGN) to the plasma membrane in yeast, bypassing the endosomal system. We have crystallized a subcomplex of the exomer coat and hope to determine its structure as a step towards understanding how it functions. At this point, our crystals are small and we have not yet tested their diffraction on a home x-ray source, and we believe CHESS beamtime will be required to collect meaningful data. We will use our CHESS beamtime to screen through our various crystal forms and cryo-protectant conditions, and with luck we will be collecting full native datasets.