Related Experiment Videos
SfbII protein, a fibronectin binding surface protein of group A streptococci, is a serum opacity factor with high
B Kreikemeyer1, D R Martin, G S Chhatwal
1GBF-National Research Center for Biotechnology, Technical University Braunschweig, Germany.
Abstract:
Serum opacity factor (SOF) is produced by group A streptococci belonging to certain M types. SOF cleaves the apolipoprotein component of the high density lipoprotein fraction of serum rendering it insoluble which in turn leads to serum opacity. SfbII protein, a fibronectin binding surface protein cloned from group A streptococci, was obtained from a strain of M75. Here we show that this protein has a second functional domain responsible for SOF activity. The fibronectin binding region was located in the C-terminal end of the protein. Deletion analysis showed that the remainder of the protein was required for SOF activity. Sequence analysis of SfbII, when compared with the published sequence of SOF22, showed 99% identity with a difference of only four amino acids. In spite of this high homology, SOF from M75 was type-specific and antibody evoked specifically inhibited only SOF produced by M75. Antibodies found in human serum following natural infection also inhibited the SOF of SfbII in a type-specific manner. The results showed that the SfbII protein from M75 is SOF with a high serotype-specific enzyme activity.
Insights
Group A streptococci produce serum opacity factor (SOF), an enzyme causing serum opacity. Researchers found the SfbII protein from M75 strain possesses this SOF activity, demonstrating type-specific enzyme function.
Area of Science:
- Microbiology
- Biochemistry
- Enzymology
Background:
- Group A streptococci produce serum opacity factor (SOF), an extracellular enzyme.
- SOF contributes to pathogenicity by altering serum lipoproteins.
- Specific M types of Streptococcus pyogenes secrete SOF.
Purpose of the Study:
- To investigate the functional domains of the SfbII protein from Streptococcus pyogenes M75.
- To characterize the serum opacity factor (SOF) activity of the SfbII protein.
- To determine the serotype specificity of the SfbII protein's SOF activity.
Main Methods:
- Cloning and expression of the SfbII protein from Streptococcus pyogenes M75.
- Deletion analysis to map functional domains of the SfbII protein.
- Enzyme activity assays to measure SOF production.
- Serological assays using specific antibodies and human serum to assess type specificity.
Main Results:
- The SfbII protein possesses a distinct functional domain responsible for serum opacity factor (SOF) activity.
- The fibronectin-binding region is located at the C-terminal end, while the SOF activity requires the rest of the protein.
- Sequence analysis revealed 99% homology with SOF22, but SOF from M75 exhibited type-specific activity.
- Antibodies generated against SOF from M75, as well as antibodies from naturally infected humans, specifically inhibited the M75 SOF activity.
Conclusions:
- The SfbII protein from Streptococcus pyogenes M75 functions as a serum opacity factor (SOF).
- This SOF exhibits high serotype-specific enzyme activity, suggesting a role in host-pathogen interactions.
- The findings highlight the dual functionality of the SfbII protein, encompassing both fibronectin binding and enzymatic activity.