| 1. |
- Chen, Gefei, et al.
(författare)
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Molecular basis for different substrate-binding sites and chaperone functions of the BRICHOS domain
- 2024
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Ingår i: Protein Science. - : John Wiley & Sons. - 0961-8368 .- 1469-896X. ; 33:7
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Tidskriftsartikel (refereegranskat)abstract
- Proteins can misfold into fibrillar or amorphous aggregates and molecular chaperones act as crucial guardians against these undesirable processes. The BRICHOS chaperone domain, found in several otherwise unrelated proproteins that contain amyloidogenic regions, effectively inhibits amyloid formation and toxicity but can in some cases also prevent non-fibrillar, amorphous protein aggregation. Here, we elucidate the molecular basis behind the multifaceted chaperone activities of the BRICHOS domain from the Bri2 proprotein. High-confidence AlphaFold2 and RoseTTAFold predictions suggest that the intramolecular amyloidogenic region (Bri23) is part of the hydrophobic core of the proprotein, where it occupies the proposed amyloid binding site, explaining the markedly reduced ability of the proprotein to prevent an exogenous amyloidogenic peptide from aggregating. However, the BRICHOS-Bri23 complex maintains its ability to form large polydisperse oligomers that prevent amorphous protein aggregation. A cryo-EM-derived model of the Bri2 BRICHOS oligomer is compatible with surface-exposed hydrophobic motifs that get exposed and come together during oligomerization, explaining its effects against amorphous aggregation. These findings provide a molecular basis for the BRICHOS chaperone domain function, where distinct surfaces are employed against different forms of protein aggregation.
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| 2. |
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| 3. |
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| 4. |
- Jiang, Wangshu
(författare)
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Of spiders, bugs, and men : Structural and functional studies of proteins involved in assembly
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Protein assembly enables complex machineries while being economical with genetic information. However, protein assembly also constitutes a potential threat to the host, and needs to be carefully regulated.Sulfate is a common source of sulfur for cysteine synthesis in bacteria. A putative sulfate permease CysZ from Escherichia coli appears much larger than its apparent molecular mass when analyzed by chromatography and native gel. Clearly CysZ undergoes homo-oligomerization. Using isothermal titration calorimetry, we confirmed that CysZ binds to its putative substrate sulfate, and also sulfite with higher affinity. CysZ-mediated sulfate transport—in both E. coli whole cells and proteoliposomes—was inhibited in the presence of sulfite, indicating a feedback inhibition mechanism.Proteus mirabilis is a Gram-negative bacterium causing urinary tract infections. Its simultaneous expression of multiple fimbriae enables colonization and biofilm formation. Fimbriae are surface appendages assembled from protein subunits, with distal adhesins specifically recognizing host-cell receptors. We present the first three structures of P. mirabilis fimbrial adhesins. While UcaD and AtfE adopt the canonical immunoglobulin-like fold, MrpH has a previously unknown fold. The coordination of Zn or Cu ion by three conserved histidine residues in MrpH is required for MrpH-dependent biofilm formation.Spider silk is an assembly of large proteins called spidroins. The N-terminal domain (NT) of spidroins senses the pH decrease along the silk spinning gland, and transits from monomer to dimer. A locked NT dimer interlinks spidroin molecules into polymers. We identified a new asymmetric dimer form of NT by x-ray crystallography. With additional evidence from small angle x-ray scattering (SAXS), we propose the asymmetric dimer as a common intermediate of NT in silk formation.Alzheimer’s disease is a life-threatening dementia, where aggregation-prone Aβ peptides self-assemble into amyloid fibrils. Bri2 BRICHOS is a molecular chaperone that efficiently delays Aβ fibrillation, and protects the region of its pro-protein with high β-propensity from aggregation. Combining SAXS and microscale thermophoresis data, we confirmed binding between Bri2 BRICHOS and its native client peptide. Using site-directed mutagenesis, we showed that three conserved tyrosine residues in Bri2 BRICHOS are important for its anti-Aβ fibrillation activity.
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| 5. |
- Jiang, Wangshu, et al.
(författare)
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Structural basis for MrpH-dependent Proteus mirabilis biofilm formation
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Proteus mirabilis is a Gram-negative uropathogen and the major causative agent in catheter-associated (CAUTI) and complicated UTIs. Mannose resistant Proteus-like fimbriae (MR/P) are crucially important for P. mirabilis infectivity and are required for biofilm formation and auto-aggregation, as well as for bladder and kidney colonisation. Here, the X-ray structure of the MR/P tip-located MrpH adhesin is reported. The structure has an unusual fold not previously observed, and contains a transition metal centre with Cu2+ or Zn2+ ligated by three conserved histidine residues and a ligand. Using metal complementation biofilm assays and site directed mutagenesis of the three histidines we show that an intact metal binding site occupied by zinc or copper is essential for MR/P-mediated biofilm formation. The studies presented here provide important clues as to the mechanism of MR/P-mediated biofilm formation and will serve as a starting point for identifying the physiological MR/P receptor(s).
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| 6. |
- Jiang, Wangshu, et al.
(författare)
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Structure of the N-terminal domain of Euprosthenops australis dragline silk suggests that conversion of spidroin dope to spider silk involves a conserved asymmetric dimer intermediate
- 2019
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Ingår i: Acta Crystallographica Section D. - : International Union of Crystallography. - 2059-7983. ; 75, s. 618-627
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Tidskriftsartikel (refereegranskat)abstract
- Spider silk is a biomaterial with exceptional mechanical toughness, and there is great interest in developing biomimetic methods to produce engineered spider silk-based materials. However, the mechanisms that regulate the conversion of spider silk proteins (spidroins) from highly soluble dope into silk are not completely understood. The N-terminal domain (NT) of Euprosthenops australis dragline silk protein undergoes conformational and quaternary-structure changes from a monomer at a pH above 7 to a homodimer at lower pH values. Conversion from the monomer to the dimer requires the protonation of three conserved glutamic acid residues, resulting in a low-pH 'locked' dimer stabilized by symmetric electrostatic interactions at the poles of the dimer. The detailed molecular events during this transition are still unresolved. Here, a 2.1 angstrom resolution crystal structure of an NT T61A mutant in an alternative, asymmetric, dimer form in which the electrostatic interactions at one of the poles are dramatically different from those in symmetrical dimers is presented. A similar asymmetric dimer structure from dragline silk of Nephila clavipes has previously been described. It is suggested that asymmetric dimers represent a conserved intermediate state in spider silk formation, and a revised 'lock-and-trigger' mechanism for spider silk formation is presented.
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| 7. |
- Jiang, Wangshu, et al.
(författare)
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Structures of two fimbrial adhesins, AtfE and UcaD, from the uropathogen Proteus mirabilis
- 2018
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Ingår i: Acta Crystallographica Section D. - 2059-7983. ; 74:Pt 11, s. 1053-1062
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Tidskriftsartikel (refereegranskat)abstract
- The important uropathogen Proteus mirabilis encodes a record number of chaperone/usher-pathway adhesive fimbriae. Such fimbriae, which are used for adhesion to cell surfaces/tissues and for biofilm formation, are typically important virulence factors in bacterial pathogenesis. Here, the structures of the receptor-binding domains of the tip-located two-domain adhesins UcaD (1.5 Å resolution) and AtfE (1.58 Å resolution) from two P. mirabilis fimbriae (UCA/NAF and ATF) are presented. The structures of UcaD and AtfE are both similar to the F17G type of tip-located fimbrial receptor-binding domains, and the structures are very similar despite having only limited sequence similarity. These structures represent an important step towards a molecular-level understanding of P. mirabilis fimbrial adhesins and their roles in the complex pathogenesis of urinary-tract infections.
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| 8. |
- Sun, Wei, et al.
(författare)
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Molecular and Biochemical Analysis of Chalcone Synthase from Freesia hybrid in Flavonoid Biosynthetic Pathway
- 2015
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:3
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Tidskriftsartikel (refereegranskat)abstract
- Chalcone synthase (CHS) catalyzes the first committed step in the flavonoid biosynthetic pathway. In this study, the cDNA (FhCHS1) encoding CHS from Freesia hybrida was successfully isolated and analyzed. Multiple sequence alignments showed that both the conserved CHS active site residues and CHS signature sequence were found in the deduced amino acid sequence of FhCHS1. Meanwhile, crystallographic analysis revealed that protein structure of FhCHS1 is highly similar to that of alfalfa CHS2, and the biochemical analysis results indicated that it has an enzymatic role in naringenin biosynthesis. Moreover, quantitative real-time PCR was performed to detect the transcript levels of FhCHS1 in flowers and different tissues, and patterns of FhCHS1 expression in flowers showed significant correlation to the accumulation patterns of anthocyanin during flower development. To further characterize the functionality of FhCHS1, its ectopic expression in Arabidopsis thaliana tt4 mutants and Petunia hybrida was performed. The results showed that overexpression of FhCHS1 in tt4 mutants fully restored the pigmentation phenotype of the seed coats, cotyledons and hypocotyls, while transgenic petunia expressing FhCHS1 showed flower color alteration from white to pink. In summary, these results suggest that FhCHS1 plays an essential role in the biosynthesis of flavonoid in Freesia hybrida and may be used to modify the components of flavonoids in other plants.
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| 9. |
- Zhang, Li, et al.
(författare)
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The Escherichia coli CysZ is a pH dependent sulfate transporter that can be inhibited by sulfite
- 2014
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Ingår i: Biochimica et Biophysica Acta. - : Elsevier BV. - 0006-3002 .- 0005-2736 .- 1879-2642. ; 1838:7, s. 16-1809
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Tidskriftsartikel (refereegranskat)abstract
- The Escherichia coli inner membrane protein CysZ mediates the sulfate uptake subsequently utilized for the synthesis of sulfur-containing compounds in cells. Here we report the purification and functional characterization of CysZ. Using Isothermal Titration Calorimetry, we have observed interactions between CysZ and its putative substrate sulfate. Additional sulfur-containing compounds from the cysteine synthesis pathway have also been analyzed for their abilities to interact with CysZ. Our results suggest that CysZ is dedicated to a specific pathway that assimilates sulfate for the synthesis of cysteine. Sulfate uptake via CysZ into E. coli whole cells and proteoliposome offers direct evidence of CysZ being able to mediate sulfate uptake. In addition, the cysteine synthesis pathway intermediate sulfite can interact directly with CysZ with higher affinity than sulfate. The sulfate transport activity is inhibited in the presence of sulfite, suggesting the existence of a feedback inhibition mechanism in which sulfite regulates sulfate uptake by CysZ. Sulfate uptake assays performed at different extracellular pH and in the presence of a proton uncoupler indicate that this uptake is driven by the proton gradient.
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