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Two-dimensional crystallization of rabbit C-reactive protein monomeric subunits
Yi Wu1, Hong-Wei Wang, Shang-Rong Ji
1Department of Biological Sciences and Biotechnology, State Key Laboratory of Biomembranes, Tsinghua University, Beijing 100084, People's Republic of China.
Summary
Modified C-reactive protein (CRP) exists physiologically. Researchers formed two crystal types (MI and MII) from monomeric CRP, revealing pH-dependent assembly and supporting modified CRP
Area of Science:
- Biochemistry
- Structural Biology
- Protein Crystallography
Background:
- C-reactive protein (CRP) is a key acute-phase protein.
- Modified CRP, a monomeric form, is hypothesized to exist physiologically.
Purpose of the Study:
- To investigate the structure and formation of monomeric CRP crystals.
- To determine if dissociated or denatured CRP subunits form ordered structures.
Main Methods:
- Size-exclusion chromatography to separate CRP subunits.
- Formation of two-dimensional crystals on lipid monolayers.
- pH-dependent crystallization experiments.
- Projection mapping of MII crystals.
Main Results:
- Two distinct two-dimensional crystal forms (MI and MII) of monomeric CRP were obtained.
- Crystal formation was pH-dependent: MI below pH 5.5, MII above pH 6.5.
- Acid-denatured CRP formed only MI crystals.
- MII crystals yielded a 2.0 nm resolution projection map.
Conclusions:
- Monomeric CRP subunits can form highly ordered two-dimensional crystals.
- The pH-dependent assembly supports distinct structural states of CRP.
- Findings provide evidence for the existence of modified CRP in vivo.