ALBERT

Description: The polyketide synthase (PKS) mega-enzyme assembly line uses a modular architecture to synthesize diverse and bioactive natural products that often constitute the core structures or complete chemical entities for many clinically approved therapeutic agents. The architecture of a full-length PKS module from the pikromycin pathway of Streptomyces venezuelae creates a reaction chamber for the intramodule acyl carrier protein (ACP) domain that carries building blocks and intermediates between acyltransferase, ketosynthase and ketoreductase active sites (see accompanying paper). Here we determine electron cryo-microscopy structures of a full-length pikromycin PKS module in three key biochemical states of its catalytic cycle. Each biochemical state was confirmed by bottom-up liquid chromatography/Fourier transform ion cyclotron resonance mass spectrometry. The ACP domain is differentially and precisely positioned after polyketide chain substrate loading on the active site of the ketosynthase, after extension to the beta-keto intermediate, and after beta-hydroxy product generation. The structures reveal the ACP dynamics for sequential interactions with catalytic domains within the reaction chamber, and for transferring the elongated and processed polyketide substrate to the next module in the PKS pathway. During the enzymatic cycle the ketoreductase domain undergoes dramatic conformational rearrangements that enable optimal positioning for reductive processing of the ACP-bound polyketide chain elongation intermediate. These findings have crucial implications for the design of functional PKS modules, and for the engineering of pathways to generate pharmacologically relevant molecules.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4074775/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4074775/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Whicher, Jonathan R -- Dutta, Somnath -- Hansen, Douglas A -- Hale, Wendi A -- Chemler, Joseph A -- Dosey, Annie M -- Narayan, Alison R H -- Hakansson, Kristina -- Sherman, David H -- Smith, Janet L -- Skiniotis, Georgios -- 1R21CA138331-01A1/CA/NCI NIH HHS/ -- DK042303/DK/NIDDK NIH HHS/ -- DK090165/DK/NIDDK NIH HHS/ -- GM076477/GM/NIGMS NIH HHS/ -- R01 DK042303/DK/NIDDK NIH HHS/ -- R01 DK090165/DK/NIDDK NIH HHS/ -- R01 GM076477/GM/NIGMS NIH HHS/ -- T32 GM008597/GM/NIGMS NIH HHS/ -- England -- Nature. 2014 Jun 26;510(7506):560-4. doi: 10.1038/nature13409. Epub 2014 Jun 18.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, USA [2] Chemical Biology Graduate Program, University of Michigan, Ann Arbor, Michigan 48109, USA [3]. ; 1] Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, USA [2]. ; 1] Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, USA [2] Department of Medicinal Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA. ; Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA. ; Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, USA. ; 1] Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, USA [2] Department of Medicinal Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA [3] Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA [4] Department of Microbiology & Immunology, University of Michigan, Ann Arbor, Michigan 48109, USA. ; 1] Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, USA [2] Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24965656" target="_blank"〉PubMed〈/a〉

Description: G-protein-coupled receptors (GPCRs) are critically regulated by beta-arrestins, which not only desensitize G-protein signalling but also initiate a G-protein-independent wave of signalling. A recent surge of structural data on a number of GPCRs, including the beta2 adrenergic receptor (beta2AR)-G-protein complex, has provided novel insights into the structural basis of receptor activation. However, complementary information has been lacking on the recruitment of beta-arrestins to activated GPCRs, primarily owing to challenges in obtaining stable receptor-beta-arrestin complexes for structural studies. Here we devised a strategy for forming and purifying a functional human beta2AR-beta-arrestin-1 complex that allowed us to visualize its architecture by single-particle negative-stain electron microscopy and to characterize the interactions between beta2AR and beta-arrestin 1 using hydrogen-deuterium exchange mass spectrometry (HDX-MS) and chemical crosslinking. Electron microscopy two-dimensional averages and three-dimensional reconstructions reveal bimodal binding of beta-arrestin 1 to the beta2AR, involving two separate sets of interactions, one with the phosphorylated carboxy terminus of the receptor and the other with its seven-transmembrane core. Areas of reduced HDX together with identification of crosslinked residues suggest engagement of the finger loop of beta-arrestin 1 with the seven-transmembrane core of the receptor. In contrast, focal areas of raised HDX levels indicate regions of increased dynamics in both the N and C domains of beta-arrestin 1 when coupled to the beta2AR. A molecular model of the beta2AR-beta-arrestin signalling complex was made by docking activated beta-arrestin 1 and beta2AR crystal structures into the electron microscopy map densities with constraints provided by HDX-MS and crosslinking, allowing us to obtain valuable insights into the overall architecture of a receptor-arrestin complex. The dynamic and structural information presented here provides a framework for better understanding the basis of GPCR regulation by arrestins.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4134437/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4134437/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Shukla, Arun K -- Westfield, Gerwin H -- Xiao, Kunhong -- Reis, Rosana I -- Huang, Li-Yin -- Tripathi-Shukla, Prachi -- Qian, Jiang -- Li, Sheng -- Blanc, Adi -- Oleskie, Austin N -- Dosey, Anne M -- Su, Min -- Liang, Cui-Rong -- Gu, Ling-Ling -- Shan, Jin-Ming -- Chen, Xin -- Hanna, Rachel -- Choi, Minjung -- Yao, Xiao Jie -- Klink, Bjoern U -- Kahsai, Alem W -- Sidhu, Sachdev S -- Koide, Shohei -- Penczek, Pawel A -- Kossiakoff, Anthony A -- Woods, Virgil L Jr -- Kobilka, Brian K -- Skiniotis, Georgios -- Lefkowitz, Robert J -- DK090165/DK/NIDDK NIH HHS/ -- GM072688/GM/NIGMS NIH HHS/ -- GM087519/GM/NIGMS NIH HHS/ -- GM60635/GM/NIGMS NIH HHS/ -- HL075443/HL/NHLBI NIH HHS/ -- HL16037/HL/NHLBI NIH HHS/ -- HL70631/HL/NHLBI NIH HHS/ -- MOP-93725/Canadian Institutes of Health Research/Canada -- NS028471/NS/NINDS NIH HHS/ -- R01 DK090165/DK/NIDDK NIH HHS/ -- R01 GM060635/GM/NIGMS NIH HHS/ -- R01 GM072688/GM/NIGMS NIH HHS/ -- R01 HL016037/HL/NHLBI NIH HHS/ -- R01 HL070631/HL/NHLBI NIH HHS/ -- R01 NS028471/NS/NINDS NIH HHS/ -- UL1 TR000430/TR/NCATS NIH HHS/ -- Howard Hughes Medical Institute/ -- England -- Nature. 2014 Aug 14;512(7513):218-22. doi: 10.1038/nature13430. Epub 2014 Jun 22.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA [2] Department of Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur 208016, India. [3]. ; 1] Life Sciences Institute and Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA [2]. ; 1] Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA [2]. ; Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA. ; Department of Chemistry, University of California at San Diego, La Jolla, California 92093, USA. ; Life Sciences Institute and Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA. ; School of Pharmaceutical &Life Sciences, Changzhou University, Changzhou, Jiangsu 213164, China. ; Terrence Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario M5S 3E1, Canada. ; Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA. ; Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637, USA. ; Department of Biochemistry and Molecular Biology, The University of Texas Medical School at Houston, Houston, Texas 77054, USA. ; 1] Department of Chemistry, University of California at San Diego, La Jolla, California 92093, USA [2]. ; Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, California 94305, USA. ; 1] Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA [2] Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA [3] Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25043026" target="_blank"〉PubMed〈/a〉