Browsing by Subject "BINDING"
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Item Open Access Allosteric modulation of nucleoporin assemblies by intrinsically disordered regions.(Science advances, 2019-11-27) Blus, Bartlomiej Jan; Koh, Junseock; Krolak, Aleksandra; Seo, Hyuk-Soo; Coutavas, Elias; Blobel, GünterIntrinsically disordered regions (IDRs) of proteins are implicated in key macromolecular interactions. However, the molecular forces underlying IDR function within multicomponent assemblies remain elusive. By combining thermodynamic and structural data, we have discovered an allostery-based mechanism regulating the soluble core region of the nuclear pore complex (NPC) composed of nucleoporins Nup53, Nic96, and Nup157. We have identified distinct IDRs in Nup53 that are functionally coupled when binding to partner nucleoporins and karyopherins (Kaps) involved in NPC assembly and nucleocytoplasmic transport. We show that the Nup53·Kap121 complex forms an ensemble of structures that destabilize Nup53 hub interactions. Our study provides a molecular framework for understanding how disordered and folded domains communicate within macromolecular complexes.Item Open Access Comparison of the molecular properties of retinitis pigmentosa P23H and N15S amino acid replacements in rhodopsin.(PloS one, 2019-01) Mitchell, James; Balem, Fernanda; Tirupula, Kalyan; Man, David; Dhiman, Harpreet Kaur; Yanamala, Naveena; Ollesch, Julian; Planas-Iglesias, Joan; Jennings, Barbara J; Gerwert, Klaus; Iannaccone, Alessandro; Klein-Seetharaman, JudithMutations in the RHO gene encoding for the visual pigment protein, rhodopsin, are among the most common cause of autosomal dominant retinitis pigmentosa (ADRP). Previous studies of ADRP mutations in different domains of rhodopsin have indicated that changes that lead to more instability in rhodopsin structure are responsible for more severe disease in patients. Here, we further test this hypothesis by comparing side-by-side and therefore quantitatively two RHO mutations, N15S and P23H, both located in the N-terminal intradiscal domain. The in vitro biochemical properties of these two rhodopsin proteins, expressed in stably transfected tetracycline-inducible HEK293S cells, their UV-visible absorption, their Fourier transform infrared, circular dichroism and Metarhodopsin II fluorescence spectroscopy properties were characterized. As compared to the severely impaired P23H molecular function, N15S is only slightly defective in structure and stability. We propose that the molecular basis for these structural differences lies in the greater distance of the N15 residue as compared to P23 with respect to the predicted rhodopsin folding core. As described previously for WT rhodopsin, addition of the cytoplasmic allosteric modulator chlorin e6 stabilizes especially the P23H protein, suggesting that chlorin e6 may be generally beneficial in the rescue of those ADRP rhodopsin proteins whose stability is affected by amino acid replacement.Item Open Access Protein prenylation restrains innate immunity by inhibiting Rac1 effector interactions.(Nature communications, 2019-09-04) Akula, Murali K; Ibrahim, Mohamed X; Ivarsson, Emil G; Khan, Omar M; Kumar, Israiel T; Erlandsson, Malin; Karlsson, Christin; Xu, Xiufeng; Brisslert, Mikael; Brakebusch, Cord; Wang, Donghai; Bokarewa, Maria; Sayin, Volkan I; Bergo, Martin ORho family proteins are prenylated by geranylgeranyltransferase type I (GGTase-I), which normally target proteins to membranes for GTP-loading. However, conditional deletion of GGTase-I in mouse macrophages increases GTP-loading of Rho proteins, leading to enhanced inflammatory responses and severe rheumatoid arthritis. Here we show that heterozygous deletion of the Rho family gene Rac1, but not Rhoa and Cdc42, reverses inflammation and arthritis in GGTase-I-deficient mice. Non-prenylated Rac1 has a high affinity for the adaptor protein Ras GTPase-activating-like protein 1 (Iqgap1), which facilitates both GTP exchange and ubiquitination-mediated degradation of Rac1. Consistently, inactivating Iqgap1 normalizes Rac1 GTP-loading, and reduces inflammation and arthritis in GGTase-I-deficient mice, as well as prevents statins from increasing Rac1 GTP-loading and cytokine production in macrophages. We conclude that blocking prenylation stimulates Rac1 effector interactions and unleashes proinflammatory signaling. Our results thus suggest that prenylation normally restrains innate immune responses by preventing Rac1 effector interactions.