Sequence and structural homologies between M. tuberculosis chaperonin 10 and the MHC class I/II peptide binding cleft

Area of Science:

• Structural biology
• Immunology
• Molecular mimicry

Background:

• Heat shock proteins (hsp10) play roles in cellular stress responses.
• Autoimmune diseases are linked to molecular mimicry, where the immune system mistakenly attacks self-antigens.
• The C-terminal region of M.tuberculosis hsp10 was hypothesized to be an independent structural domain.

Purpose of the Study:

• To synthesize and characterize a peptide representing the C-terminal half of M.tuberculosis hsp10.
• To investigate potential structural and functional relationships between hsp10 and human leukocyte antigens (MHC).
• To explore the role of molecular mimicry in autoimmune diseases involving hsp10.

Main Methods:

• Peptide synthesis of M.tuberculosis hsp10 C-terminal region.
• Circular dichroism (CD) spectroscopy to study protein folding.
• Aggregation studies.
• 3D structural modeling.
• Sequence homology analysis.

Main Results:

• The synthesized peptide confirmed the C-terminal half of hsp10 as an independent structural region.
• The peptide exhibited significant sequence homology (40-50%) with MHC class I and II antigens.
• CD studies revealed the peptide adopts an anti-parallel beta-sheet fold at acidic pH.
• A 3D model showed the peptide possesses a "W" fold similar to that in the MHC peptide-binding groove.

Conclusions:

• The structural mimicry between M.tuberculosis hsp10 peptide and MHC antigens supports the hypothesis of molecular mimicry in autoimmune disease pathogenesis.
• These findings suggest a potential evolutionary relationship between heat shock proteins and MHC antigens.