| 1. |
- Patrick, Joan, 1987-, et al.
(författare)
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Dilute Bicelles for Glycosyltransferase Studies, Novel Bicelles with Phosphatidylinositol
- 2024
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Ingår i: Journal of Physical Chemistry B. - 1520-6106 .- 1520-5207.
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Tidskriftsartikel (refereegranskat)abstract
- Solution-state NMR can be used to study protein- lipid interactions, in particular, the effect that proteins have on lipids. One drawback is that only small assemblies can be studied, and therefore, fast-tumbling bicelles are commonly used. Bicelles contain a lipid bilayer that is solubilized by detergents. A complication is that they are only stable at high concentrations, exceeding the CMC of the detergent. This issue has previously been addressed by introducing a detergent (Cyclosfos-6) with a substantially lower CMC. Here, we developed a set of bicelles using this detergent for studies of membrane-associated mycobacterial proteins, for example, PimA, a key enzyme for bacterial growth. To mimic the lipid composition of mycobacterial membranes, PI, PG, and PC lipids were used. Diffusion NMR was used to characterize the bicelles, and spin relaxation was used to measure the dynamic properties of the lipids. The results suggest that bicelles are formed, although they are smaller than conventional bicelles. Moreover, we studied the effect of MTSL-labeled PimA on bicelles containing PI and PC. The paramagnetic label was shown to have a shallow location in the bicelle, affecting the glycerol backbone of the lipids. We foresee that these bicelles will be useful for detailed studies of protein-lipid interactions.
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| 2. |
- Patrick, Joan, 1987-, et al.
(författare)
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Lipid- and substrate-induced conformational and dynamic changes in a glycosyltransferase involved in E. coli LPS synthesis revealed by 19F and 31P NMR
- 2023
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Ingår i: Biochimica et Biophysica Acta - Biomembranes. - : Elsevier. - 0005-2736 .- 1879-2642. ; 1865:8
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Tidskriftsartikel (refereegranskat)abstract
- WaaG is a glycosyltransferase (GT) involved in the synthesis of the bacterial cell wall, and in Escherichia coli it catalyzes the transfer of a glucose moiety from the donor substrate UDP-glucose onto the nascent lipopolysaccharide (LPS) molecule which when completed constitutes the major component of the bacterium's outermost defenses. Similar to other GTs of the GT-B fold, having two Rossman-like domains connected by a short linker, WaaG is believed to undergo complex inter-domain motions as part of its function to accommodate the nascent LPS and UDP-glucose in the catalytic site located in the cleft between the two domains. As the nascent LPS is bulky and membrane-bound, WaaG is a peripheral membrane protein, adding to the complexity of studying the enzyme in a biologically relevant environment. Using specific 5-fluoro-Trp labelling of native and inserted tryptophans and 19F NMR we herein studied the dynamic interactions of WaaG with lipids using bicelles, and with the donor substrate. Line-shape changes when bicelles are added to WaaG show that the dynamic behavior is altered when binding to the model membrane, while a chemical shift change indicates an altered environment around a tryptophan located in the C-terminal domain of WaaG upon interaction with UDP-glucose or UDP. A lipid-bound paramagnetic probe was used to confirm that the membrane interaction is mediated by a loop region located in the N-terminal domain. Furthermore, the hydrolysis of the donor substrate by WaaG was quantified by 31P NMR.
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| 3. |
- Patrick, Joan, et al.
(författare)
-
Dilute Bicelles for Glycosyltransferase Studies, Novel Bicelles with Phosphatidylinositol
- 2022
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 126:30, s. 5655-5666
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Tidskriftsartikel (refereegranskat)abstract
- Solution-state NMR can be used to study protein–lipid interactions, in particular, the effect that proteins have on lipids. One drawback is that only small assemblies can be studied, and therefore, fast-tumbling bicelles are commonly used. Bicelles contain a lipid bilayer that is solubilized by detergents. A complication is that they are only stable at high concentrations, exceeding the CMC of the detergent. This issue has previously been addressed by introducing a detergent (Cyclosfos-6) with a substantially lower CMC. Here, we developed a set of bicelles using this detergent for studies of membrane-associated mycobacterial proteins, for example, PimA, a key enzyme for bacterial growth. To mimic the lipid composition of mycobacterial membranes, PI, PG, and PC lipids were used. Diffusion NMR was used to characterize the bicelles, and spin relaxation was used to measure the dynamic properties of the lipids. The results suggest that bicelles are formed, although they are smaller than “conventional” bicelles. Moreover, we studied the effect of MTSL-labeled PimA on bicelles containing PI and PC. The paramagnetic label was shown to have a shallow location in the bicelle, affecting the glycerol backbone of the lipids. We foresee that these bicelles will be useful for detailed studies of protein–lipid interactions.
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| 4. |
- Pettersson, Pontus, 1987-
(författare)
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Structure, dynamics and lipid interaction of membrane-associated proteins
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A research topic within the field of molecular biophysics is the structure-function relationship of proteins. Membrane proteins are a large, diverse group of biological macromolecules that perform many different and essential functions for the cell. Despite the abundance and importance of membrane proteins, high-resolution 3D structures from this class of proteins are underrepresented among all yet determined structures. The limited amount of data for membrane proteins hints about the higher difficulty associated with studies of this group of molecules. The determination of an atomic resolution structure is often a long process in which several obstacles need to be overcome, in particular for membrane proteins.Solution-state nuclear magnetic resonance (NMR) is a powerful measurement technique that can provide high-resolution data on the structure and dynamics of biological macromolecules, and is suitable for studies of small, dynamic membrane proteins. However, even with solution-state NMR, the membrane proteins need to be investigated in environments that are sometimes severely compromising for the protein’s native structure and function. In order to evaluate the biological significance of results obtained under such artificial conditions, supporting data from experiments in more realistic membrane models, obtained using NMR and other biophysical methods, is of great importance.The work presented in this thesis concerns studies of four membrane proteins: WaaG, Rcf1, Rcf2 and TatA. These proteins have very different characteristics in terms of their sizes and expected membrane interactions, and were accordingly found to be differently affected by the model membranes in which they were studied. Our results illustrate both the current possibilities and limitations of solution-state NMR for studying membrane proteins, and highlight the benefits of an approach where several membrane mimicking systems and measurements techniques are used in combination to arrive at correct conclusions on the properties of proteins.
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| 5. |
- Scaletti, Emma Rose, et al.
(författare)
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Structural and functional insights into the Pseudomonas aeruginosa glycosyltransferase WaaG and the implications for lipopolysaccharide biosynthesis
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The glycosyltransferase WaaG in Pseudomonas aeruginosa (PaWaaG) is involved in synthesis of the core region of lipopolysaccharides. It is a promising target for developing adjuvants that could help in the uptake of antibiotics. Herein we have determined structures of PaWaaG in complex with the nucleotide-sugars UDP-glucose, UDP-galactose and UDP-GalNAc. Structural comparison with the homologue from Escherichia coli (EcWaaG) revealed five key differences in the sugar binding pocket. Solution-state NMR analysis showed that wildtype PaWaaG specifically hydrolyzes UDP-GalNAc and unlike EcWaaG, does not hydrolyze UDP-glucose. Furthermore, we found that a PaWaaG mutant (Y97F/T208R/N282A/T283A/T285I) designed to resemble the EcWaaG sugar binding site, only hydrolyzed UDP-glucose, underscoring the importance of the identified amino acids in substrate specificity. However, neither wildtype PaWaaG nor the PaWaaG mutant capable of hydrolyzing UDP-glucose was able to complement an E. coli ΔwaaG strain, indicating that more remains to be uncovered about the function of PaWaaG in vivo. This structural and biochemical information will guide future structure-based drug design efforts targeting PaWaaG.
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