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Thomas GM, Wu Y, Leite W, Pingali SV, Weiss KL, Grant AJ, Diggs MW, Schmidt-Krey I, Gutishvili G, Gumbart JC, Urban VS, Lieberman RL. SANS reveals lipid-dependent oligomerization of an intramembrane aspartyl protease from H. volcanii. Biophys J 2024; 123:1846-1856. [PMID: 38824390 PMCID: PMC11267423 DOI: 10.1016/j.bpj.2024.05.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Revised: 05/05/2024] [Accepted: 05/29/2024] [Indexed: 06/03/2024] Open
Abstract
Reactions that occur within the lipid membrane involve, at minimum, ternary complexes among the enzyme, substrate, and lipid. For many systems, the impact of the lipid in regulating activity or oligomerization state is poorly understood. Here, we used small-angle neutron scattering (SANS) to structurally characterize an intramembrane aspartyl protease (IAP), a class of membrane-bound enzymes that use membrane-embedded aspartate residues to hydrolyze transmembrane segments of biologically relevant substrates. We focused on an IAP ortholog from the halophilic archaeon Haloferax volcanii (HvoIAP). HvoIAP purified in n-dodecyl-β-D-maltoside (DDM) fractionates on size-exclusion chromatography (SEC) as two fractions. We show that, in DDM, the smaller SEC fraction is consistent with a compact HvoIAP monomer. Molecular dynamics flexible fitting conducted on an AlphaFold2-generated monomer produces a model in which loops are compact alongside the membrane-embedded helices. In contrast, SANS data collected on the second SEC fraction indicate an oligomer consistent with an elongated assembly of discrete HvoIAP monomers. Analysis of in-line SEC-SANS data of the HvoIAP oligomer, the first such experiment to be conducted on a membrane protein at Oak Ridge National Lab (ORNL), shows a diversity of elongated and spherical species, including one consistent with the tetrameric assembly reported for the Methanoculleus marisnigri JR1 IAP crystal structure not observed previously in solution. Reconstitution of monomeric HvoIAP into bicelles increases enzyme activity and results in the assembly of HvoIAP into a species with similar dimensions as the ensemble of oligomers isolated from DDM. Our study reveals lipid-mediated HvoIAP self-assembly and demonstrates the utility of in-line SEC-SANS in elucidating oligomerization states of small membrane proteins.
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Affiliation(s)
- Gwendell M Thomas
- School of Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, Georgia
| | - Yuqi Wu
- School of Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, Georgia
| | - Wellington Leite
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee
| | | | - Kevin L Weiss
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee
| | - Arshay J Grant
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia
| | - Monneh W Diggs
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia
| | - Ingeborg Schmidt-Krey
- School of Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, Georgia; School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia
| | | | - James C Gumbart
- School of Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, Georgia; School of Physics, Georgia Institute of Technology, Atlanta, Georgia
| | - Volker S Urban
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee.
| | - Raquel L Lieberman
- School of Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, Georgia.
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Keller MJ, Zhang Q, Qian S, Sanders BC, O'Neill HM, Hettich RL. Characterization of the In Vivo Deuteration of Native Phospholipids by Mass Spectrometry Yields Guidelines for Their Regiospecific Customization. Anal Chem 2024; 96:212-219. [PMID: 38150504 DOI: 10.1021/acs.analchem.3c03750] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2023]
Abstract
Customization of deuterated biomolecules is vital for many advanced biological experiments including neutron scattering. However, because it is challenging to control the proportion and regiospecificity of deuterium incorporation in live systems, often only two or three synthetic lipids are mixed together to form simplistic model membranes. This limits the applicability and biological accuracy of the results generated with these synthetic membranes. Despite some limited prior examination of deuterating Escherichia coli lipids in vivo, this approach has not been widely implemented. Here, an extensive mass spectrometry-based profiling of E. coli phospholipid deuteration states with several different growth media was performed, and a computational method to describe deuterium distributions with a one-number summary is introduced. The deuteration states of 36 lipid species were quantitatively profiled in 15 different growth conditions, and tandem mass spectrometry was used to reveal deuterium localization. Regressions were employed to enable the prediction of lipid deuteration for untested conditions. Small-angle neutron scattering was performed on select deuterated lipid samples, which validated the deuteration states calculated from the mass spectral data. Based on these experiments, guidelines for the design of specifically deuterated phospholipids are described. This unlocks even greater capabilities from neutron-based techniques, enabling experiments that were formerly impossible.
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Affiliation(s)
- Matthew J Keller
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- UT-ORNL Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Qiu Zhang
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Shuo Qian
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- The Second Target Station Project of SNS, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Brian C Sanders
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Hugh M O'Neill
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Robert L Hettich
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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Lakey JH, Paracini N, Clifton LA. Exploiting neutron scattering contrast variation in biological membrane studies. BIOPHYSICS REVIEWS 2022; 3:021307. [PMID: 38505417 PMCID: PMC10903484 DOI: 10.1063/5.0091372] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Accepted: 05/03/2022] [Indexed: 03/21/2024]
Abstract
Biological membranes composed of lipids and proteins are central for the function of all cells and individual components, such as proteins, that are readily studied by a range of structural approaches, including x-ray crystallography and cryo-electron microscopy. However, the study of complex molecular mixtures within the biological membrane structure and dynamics requires techniques that can study nanometer thick molecular bilayers in an aqueous environment at ambient temperature and pressure. Neutron methods, including scattering and spectroscopic approaches, are useful since they can measure structure and dynamics while also being able to penetrate sample holders and cuvettes. The structural approaches, such as small angle neutron scattering and neutron reflectometry, detect scattering caused by the difference in neutron contrast (scattering length) between different molecular components such as lipids or proteins. Usually, the bigger the contrast, the clearer the structural data, and this review uses examples from our research to illustrate how contrast can be increased to allow the structures of individual membrane components to be resolved. Most often this relies upon the use of deuterium in place of hydrogen, but we also discuss the use of magnetic contrast and other elements with useful scattering length values.
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Affiliation(s)
- Jeremy H. Lakey
- Institute for Cell and Molecular Bioscience, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, United Kingdom
| | - Nicolò Paracini
- Biofilms Research Center for Biointerfaces, Malmö University, Per Albin Hanssons väg 35, 21432 Malmö, Sweden
| | - Luke A. Clifton
- ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, United Kingdom
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