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Biochemical and Structural Characterization of the Carbohydrate Transport Substrate-binding-protein SP0092
Published on: October 2, 2017
Genome-based identification and characterization of a putative mucin-binding protein from the surface of
Daniela Bumbaca1, James E Littlejohn, Hannah Nayakanti
1Center for Immunobiology and Vaccine Development, Children's Hospital Oakland Research Institute, Oakland, California 94609, USA.
Abstract:
Streptococcus pneumoniae open reading frame SP1492 encodes a surface protein that contains a novel conserved domain similar to the repeated fragments of mucin-binding proteins from lactobacilli and lactococci. To investigate the functional role(s) of this protein and its potential adhesive properties, the surface-exposed region of SP1492 was expressed in Escherichia coli, purified to homogeneity, and partially characterized by biophysical and immunological methods. Circular dichroism and sedimentation measurements confirmed that SP1492 is an all-beta protein that exists in solution as a monomer. The SP1492 protein has been shown to be expressed by S. pneumoniae and was experimentally localized to its surface. The protein functional domain binds to mucins II and III from porcine stomach and to purified submaxillary bovine gland mucin. It appears to be one of the very few unambiguous pneumococcal adhesin molecules known to date. A hypothetical model constructed by ab initio techniques predicts a novel beta-sandwich protein structure.
Insights
Streptococcus pneumoniae SP1492 protein is a surface adhesin that binds to mucins. This finding identifies a novel pneumococcal adhesin molecule with potential implications for understanding bacterial adhesion.
Area of Science:
- Microbiology
- Molecular Biology
- Structural Biology
Background:
- Streptococcus pneumoniae (S. pneumoniae) is a significant human pathogen.
- Understanding bacterial adhesion mechanisms is crucial for combating infections.
- SP1492 is an S. pneumoniae open reading frame encoding a surface protein.
Purpose of the Study:
- To investigate the functional roles and adhesive properties of the S. pneumoniae SP1492 protein.
- To characterize the novel conserved domain within SP1492.
- To determine if SP1492 acts as a pneumococcal adhesin.
Main Methods:
- Expression and purification of the surface-exposed region of SP1492 in Escherichia coli.
- Biophysical characterization using circular dichroism and sedimentation measurements.
- Immunological methods and mucin-binding assays with purified mucins.
Main Results:
- SP1492 was confirmed as an all-beta protein existing as a monomer in solution.
- The protein was experimentally localized to the surface of S. pneumoniae.
- The functional domain of SP1492 demonstrated binding to porcine and bovine mucins.
Conclusions:
- SP1492 functions as a mucin-binding protein.
- This protein represents a novel and unambiguous pneumococcal adhesin.
- A predicted beta-sandwich structure suggests a unique protein fold for this adhesin.
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