Ab-initio SAXS Reconstruction of the Envelope Structure of Immunoglobulin IgG₁

Introduction

One of the DANNALAB’s research directions relates to the reconstruction of protein and peptide structures in close-to-natural biological environments.

Type IgG₁ is the most abundant type of immunoglobulin in serum and the recombinant monoclonal IgG1 antibody belongs to a major class of biopharmaceuticals. The function of the protein is closely defined by its actual structure and conformations. The reconstruction of the IgG₁ structure in a close-to-natural environment is an important step in assessing its stability and conformational space.

SAXS Experiment

SAXS measurements were conducted at room temperature with the use of 0.25% wt. solution of IgG₁ in a buffer. The low-resolution envelope structure of IgG₁ was determined by Ab-initio reconstruction with the use of the DAMMIN software package of EMBL.

Results

Figure 1 represents the reconstructed structure (top) compared to the high-resolution structure 1IGY obtained by X-ray crystallography ^[1] (bottom).

The estimated molecular mass for the reconstructed structure was determined to be 145 kDa compared to 146kDa of the high-resolution structure.

Figure 1. IgG₁ structure reconstructed from SAXS solution scattering experiment (top) compared with the 1IGY high-resolution model (bottom) ^[1]

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References

[1] 1IGY entry in pdb database (www.pdb.org)