@article {67990, title = {Cryo-EM structures of the human GATOR1-Rag-Ragulator complex reveal a spatial-constraint regulated GAP mechanism.}, journal = {Molecular Cell}, volume = {36}, year = {2022}, month = {2022 May 01}, abstract = {

mTORC1 controls cellular metabolic processes in response to nutrient availability. Amino acid signals are transmitted to mTORC1 through the Rag GTPases, which are localized on the lysosomal surface by the Ragulator complex. The Rag GTPases receive amino acid signals from multiple upstream regulators. One negative regulator, GATOR1, is a GTPase activating protein (GAP) for RagA. GATOR1 binds to the Rag GTPases via two modes: an inhibitory mode and a GAP mode. How these two binding interactions coordinate to process amino acid signals is unknown. Here, we resolved three cryo-EM structural models of the GATOR1-Rag-Ragulator complex, with the Rag-Ragulator subcomplex occupying the inhibitory site, the GAP site, and both binding sites simultaneously. When the Rag GTPases bind to GATOR1 at the GAP site, both Rag subunits contact GATOR1 to coordinate their nucleotide loading states. These results reveal a potential GAP mechanism of GATOR1 during the mTORC1 inactivation process.

}, issn = {1097-4164}, doi = {10.1016/j.molcel.2022.03.002}, author = {Egri, Shawn B and Ouch, Christna and Chou, Hui-Ting and Yu, Zhiheng and Song, Kangkang and Xu, Chen and Shen, Kuang} } @article {48093, title = {Structure of a Holliday junction complex reveals mechanisms governing a highly regulated DNA transaction.}, journal = {eLife}, volume = {5}, year = {2016}, month = {2016 May 25}, abstract = {

The molecular machinery responsible for DNA expression, recombination, and compaction has been difficult to visualize as functionally complete entities due to their combinatorial and structural complexity. We report here the structure of the intact functional assembly responsible for regulating and executing a site-specific DNA recombination reaction. The assembly is a 240-bp Holliday junction (HJ) bound specifically by 11 protein subunits. This higher-order complex is a key intermediate in the tightly regulated pathway for the excision of bacteriophage λ viral DNA out of the E. coli host chromosome, an extensively studied paradigmatic model system for the regulated rearrangement of DNA. Our results provide a structural basis for pre-existing data describing the excisive and integrative recombination pathways, and they help explain their regulation.

}, issn = {2050-084X}, doi = {10.7554/eLife.14313}, author = {Laxmikanthan, Gurunathan and Xu, Chen and Brilot, Axel F and Warren, David and Steele, Lindsay and Seah, Nicole and Tong, Wenjun and Grigorieff, Nikolaus and Landy, Arthur and Van Duyne, Gregory D} } @article {6341, title = {Pentameric assembly of potassium channel tetramerization domain-containing protein 5.}, journal = {Journal of Molecular Biology}, volume = {387}, year = {2009}, month = {2009 Mar 20}, pages = {175-91}, abstract = {

We report the X-ray crystal structure of human potassium channel tetramerization domain-containing protein 5 (KCTD5), the first member of the family to be so characterized. Four findings were unexpected. First, the structure reveals assemblies of five subunits while tetramers were anticipated; pentameric stoichiometry is observed also in solution by scanning transmission electron microscopy mass analysis and analytical ultracentrifugation. Second, the same BTB (bric-a-brac, tramtrack, broad complex) domain surface mediates the assembly of five KCTD5 and four voltage-gated K(+) (Kv) channel subunits; four amino acid differences appear crucial. Third, KCTD5 complexes have well-defined N- and C-terminal modules separated by a flexible linker that swivels by approximately 30 degrees; the C-module shows a new fold and is required to bind Golgi reassembly stacking protein 55 with approximately 1 microM affinity, as judged by surface plasmon resonance and ultracentrifugation. Fourth, despite the homology reflected in its name, KCTD5 does not impact the operation of Kv4.2, Kv3.4, Kv2.1, or Kv1.2 channels.

}, keywords = {Amino Acid, Amino Acid Sequence, Biopolymers, Crystallography, Humans, Models, Molecular, Molecular Sequence Data, Potassium Channels, Protein Conformation, Sequence Homology, Static Electricity, Surface Plasmon Resonance, X-Ray}, issn = {1089-8638}, doi = {10.1016/j.jmb.2009.01.030}, author = {Dementieva, Irina S and Tereshko, Valentina and McCrossan, Zoe A and Solomaha, Elena and Araki, Daniel and Xu, Chen and Grigorieff, Nikolaus and Goldstein, Steve A N} }