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.
Keywords:
ABC transporters; Streptococcus pneumoniae; carbohydrate uptake; substrate-binding protein SP0092.
MeSH terms
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Amino Acid Sequence
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Bacterial Proteins / chemistry*
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Bacterial Proteins / genetics
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Bacterial Proteins / metabolism
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Binding Sites
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Cloning, Molecular
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Crystallography, X-Ray
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Escherichia coli / genetics
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Escherichia coli / metabolism
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Gene Expression
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Models, Molecular
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Oligosaccharides / chemistry*
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Oligosaccharides / metabolism
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Plasmids / chemistry
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Plasmids / metabolism
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Protein Binding
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Protein Conformation, alpha-Helical
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Protein Conformation, beta-Strand
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Protein Interaction Domains and Motifs
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Protein Multimerization
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Receptors, Cell Surface / chemistry*
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Receptors, Cell Surface / genetics
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Receptors, Cell Surface / metabolism
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Recombinant Proteins / chemistry
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Recombinant Proteins / genetics
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Recombinant Proteins / metabolism
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Sequence Alignment
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Sequence Homology, Amino Acid
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Streptococcus pneumoniae / chemistry*
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Streptococcus pneumoniae / metabolism
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Substrate Specificity
Substances
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Bacterial Proteins
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Oligosaccharides
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Receptors, Cell Surface
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Recombinant Proteins
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saccharide-binding proteins