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High level expression and dimer characterization of the S100 EF-hand proteins, migration inhibitory factor-related
1Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
Abstract:
The phenotypical and functional heterogeneity of different macrophage subpopulations are defined by discrete changes in the expression of two S100 calcium-binding proteins, migration inhibitory factor-related proteins (MRPs) 8 and 14. To further our understanding of MRP8 and MRP14 in the developmental stages of inflammatory responses, overexpression of the MRPs was obtained through a combination of a T7-based expression vector and the Escherichia coli BL21 (DE3) cell line. An efficient, two-step chromatographic protocol was then developed for rapid, facile purification. Extensive biophysical characterization and chemical cross-linking experiments show that MRP8 and MRP14 form oligomers with a strong preference to associate as a heterodimer. Heteronuclear NMR experiments indicate that a specific well packed dimer is formed only in equimolar mixtures of the two proteins. Our results suggest that there is a unique complementarity in the interface of the MRP8/MRP14 complex that cannot be fully reproduced in the MRP8 and MRP14 homodimers.
Insights
Migration inhibitory factor-related proteins (MRPs) 8 and 14, key in macrophage function, primarily form heterodimers. This specific complex formation, revealed by NMR, highlights unique complementarity essential for their biological roles.
Area of Science:
- Biochemistry
- Molecular Biology
- Immunology
Background:
- Macrophage heterogeneity is linked to S100 calcium-binding proteins, migration inhibitory factor-related proteins (MRPs) 8 and 14.
- Understanding MRP8 and MRP14 roles in inflammation requires studying their interactions.
Purpose of the Study:
- To investigate the oligomeric state and complex formation of MRP8 and MRP14.
- To elucidate the structural basis of MRP8/MRP14 interactions.
Main Methods:
- Overexpression of MRP8 and MRP14 using a T7-based expression vector in Escherichia coli BL21 (DE3).
- Two-step chromatographic purification.
- Biophysical characterization including chemical cross-linking and Heteronuclear NMR spectroscopy.
Main Results:
- MRP8 and MRP14 form stable oligomers with a strong preference for heterodimerization.
- NMR data indicate a well-packed heterodimer forms specifically in equimolar protein mixtures.
- Homodimers of MRP8 and MRP14 show less defined interfaces compared to the heterodimer.
Conclusions:
- MRP8 and MRP14 preferentially form a heterodimer, suggesting specific functional implications.
- The unique complementarity at the MRP8/MRP14 interface is critical for their complex formation.
- These findings provide insights into the molecular mechanisms underlying macrophage functional heterogeneity.