Related Experiment Video
Updated: Mar 9, 2026
Biochemical and Structural Characterization of the Carbohydrate Transport Substrate-binding-protein SP0092
Published on: October 2, 2017
Structural characterization of the Streptococcus pneumoniae carbohydrate substrate-binding protein SP0092
Simone Culurgioni1, Minzhe Tang1, Martin Austin Walsh1
1Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, England.
Insights
Streptococcus pneumoniae imports carbohydrates using SP0092, a protein that forms a dimer. This dimer structure may regulate how the bacteria take up essential sugars.
Area of Science:
- Microbiology and Structural Biology
- Bacterial Pathogenesis and Metabolism
Background:
- Streptococcus pneumoniae is a significant global pathogen causing substantial morbidity and mortality, particularly in vulnerable populations like infants and the elderly.
- This bacterium is metabolically dependent on carbohydrates, allocating a substantial portion of its transport systems to their import.
Purpose of the Study:
- To elucidate the structural basis of carbohydrate uptake in Streptococcus pneumoniae.
- To characterize the substrate-binding protein SP0092 and its role in nutrient acquisition.
Main Methods:
- Determined the high-resolution crystal structure of the substrate-binding protein SP0092 at 1.61 Å.
- Analyzed the oligomeric state of SP0092 in solution and in its crystalline form.
- Investigated the conformation of SP0092 in the absence of its carbohydrate ligand.
Main Results:
- SP0092 belongs to a novel subclass G of substrate-binding proteins, featuring a large ligand-binding pocket capable of accommodating complex oligosaccharides.
- SP0092 exists as a dimer in solution, and its crystal structure reveals a domain-swapped dimer.
- Monomer subunits adopt a closed conformation, even without a bound ligand, potentially influenced by dimer formation.
Conclusions:
- The structural insights into SP0092 provide a molecular understanding of carbohydrate import mechanisms in Streptococcus pneumoniae.
- Dimerization of SP0092 may represent a regulatory mechanism controlling carbohydrate uptake in response to environmental cues or nutrient availability.
Abstract:
Streptococcus pneumoniae is an opportunistic respiratory pathogen that remains a major cause of morbidity and mortality globally, with infants and the elderly at the highest risk. S. pneumoniae relies entirely on carbohydrates as a source of carbon and dedicates a third of all uptake systems to carbohydrate import. The structure of the carbohydrate-free substrate-binding protein SP0092 at 1.61 Å resolution reveals it to belong to the newly proposed subclass G of substrate-binding proteins, with a ligand-binding pocket that is large enough to accommodate complex oligosaccharides. SP0092 is a dimer in solution and the crystal structure reveals a domain-swapped dimer with the monomer subunits in a closed conformation but in the absence of carbohydrate ligand. This closed conformation may be induced by dimer formation and could be used as a mechanism to regulate carbohydrate uptake.
