Streptococcus pneumoniae secretes a glyceraldehyde-3-phosphate dehydrogenase, which binds haemoglobin and haem

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Iron Metabolism

Background:

• Streptococcus pneumoniae causes serious infections like septicemia and respiratory illness in children.
• This bacterium requires iron for survival, obtaining it from host sources like hemoglobin (Hb) and heme.
• Previous research identified only two membrane proteins involved in Hb binding by S. pneumoniae.

Purpose of the Study:

• To investigate whether S. pneumoniae secretes proteins to scavenge iron from hemoglobin or heme.
• To explore alternative iron acquisition strategies employed by S. pneumoniae.

Main Methods:

• Culturing S. pneumoniae with various iron sources, including iron, Hb, and heme.
• Purification and characterization of secreted bacterial proteins.
• Identification of the secreted protein using mass spectrometry.

Main Results:

• Bacterial growth was supported by iron, Hb, and heme.
• A 38 kDa protein was expressed and secreted by S. pneumoniae.
• This secreted protein was purified and identified as glyceraldehyde-3-phosphate dehydrogenase, exhibiting Hb and heme-binding capabilities.

Conclusions:

• S. pneumoniae secretes glyceraldehyde-3-phosphate dehydrogenase, a novel Hb and heme-binding protein.
• This secreted protein likely plays a significant role in the bacterium's ability to acquire essential iron sources.
• The findings suggest a new mechanism contributing to the virulence and infectivity of S. pneumoniae.