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Fibronectin-binding proteins secreted by Mycobacterium avium
1School of Dentistry, Nagasaki University, Sakamoto, Nagasaki City, Japan.
Summary
Mycobacterium avium utilizes fibronectin-binding proteins, including the Antigen 85 complex and MPA51, for infection. These proteins are crucial virulence factors for this opportunistic pathogen, particularly in AIDS patients.
Area of Science:
- Microbiology
- Immunology
- Biochemistry
Background:
- Mycobacterium avium is an opportunistic pathogen frequently infecting individuals with acquired immune deficiency syndrome (AIDS).
- Fibronectin (FN), an extracellular matrix protein, acts as a virulence factor for various bacterial pathogens by mediating attachment to mucosal surfaces.
Purpose of the Study:
- To identify and characterize fibronectin-binding proteins present in the culture filtrate of Mycobacterium avium.
- To elucidate the specific M. avium proteins that interact with fibronectin.
Main Methods:
- Proteins from M. avium culture filtrate were separated using two-dimensional electrophoresis (2DE).
- Proteins were transferred to a polyvinylidene difluoride membrane and incubated with fibronectin.
- Western blotting with an anti-fibronectin antibody was employed to detect fibronectin-binding proteins.
- N-terminal amino acid sequencing was performed on identified fibronectin-binding spots.
Main Results:
- Fibronectin bound to five distinct protein spots with molecular masses of 33 kDa, 32 kDa, 31 kDa, 30 kDa, and 25 kDa.
- The 33 kDa spot was identified as antigen 85 (Ag 85) C.
- The 32 kDa and 31 kDa spots corresponded to Ag 85 A or Ag 85 B, while the 30 kDa spot was identified as Ag 85 B.
- The 25 kDa spot was identified as MPA51 (M. avium MPB51).
Conclusions:
- Fibronectin exclusively binds to the Antigen 85 complex (Ag 85 A, B, and C) and MPA51 in Mycobacterium avium.
- These fibronectin-binding proteins are likely key virulence factors for M. avium, contributing to its pathogenesis, particularly in immunocompromised individuals.