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Updated: Jun 9, 2026
From Constructs to Crystals – Towards Structure Determination of β-barrel Outer Membrane Proteins
Published on: July 4, 2016
Crystallization and preliminary crystallographic characterization of the iron-regulated outer membrane lipoprotein
Ekaterina Sviridova1, Ladislav Bumba, Pavlina Rezacova
1Institute of Physical Biology, University of South Bohemia Ceske Budejovice, Zamek 136, 373 33 Nove Hrady, Czech Republic.
Abstract:
Fe-regulated protein D (FrpD) is a Neisseria meningitidis outer membrane lipoprotein that may be involved in the anchoring of the secreted repeat in toxins (RTX) protein FrpC to the outer bacterial membrane. However, the function and biological roles of the FrpD and FrpC proteins remain unknown. Native and selenomethionine-substituted variants of recombinant FrpD43-271 protein were crystallized using the sitting-drop vapour-diffusion method. Diffraction data were collected to a resolution of 2.25 A for native FrpD43-271 protein and to a resolution of 2.00 A for selenomethionine-substituted FrpD43-271 (SeMet FrpD43-271) protein. The crystals of native FrpD43-271 protein belonged to the hexagonal space group P6(2) or P6(4), while the crystals of SeMet FrpD43-271 protein belonged to the primitive orthorhombic space group P2(1)2(1)2(1).
Insights
Neisseria meningitidis outer membrane proteins FrpD and FrpC roles are unknown. Researchers crystallized FrpD43-271 variants, enabling structural studies for understanding its function in bacterial outer membrane anchoring.
Area of Science:
- Microbiology
- Structural Biology
- Biochemistry
Background:
- Fe-regulated protein D (FrpD) is an outer membrane lipoprotein in Neisseria meningitidis.
- FrpD may anchor the RTX protein FrpC to the bacterial outer membrane, but its function is unknown.
- The biological roles of both FrpD and FrpC remain to be elucidated.
Purpose of the Study:
- To investigate the structural properties of the Neisseria meningitidis FrpD protein.
- To obtain high-resolution structural data for recombinant FrpD43-271 for future functional studies.
Main Methods:
- Recombinant FrpD43-271 protein variants (native and selenomethionine-substituted) were expressed.
- Crystallization was achieved using the sitting-drop vapour-diffusion method.
- X-ray diffraction data were collected to high resolutions (2.25 Å for native, 2.00 Å for SeMet).
Main Results:
- Crystals of native FrpD43-271 belonged to space group P6(2) or P6(4).
- Crystals of selenomethionine-substituted FrpD43-271 (SeMet FrpD43-271) belonged to space group P2(1)2(1)2(1).
- High-resolution diffraction data were successfully obtained for both protein variants.
Conclusions:
- The successful crystallization and diffraction data collection provide a foundation for determining the 3D structure of FrpD.
- Structural insights into FrpD may reveal its role in anchoring FrpC and its broader biological functions in Neisseria meningitidis.
- Further structural and biochemical studies are warranted to fully understand FrpD and FrpC functions.
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