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PDBsum entry 2xd2
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Sugar binding protein
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PDB id
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2xd2
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References listed in PDB file
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Key reference
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Title
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The molecular basis of glycogen breakdown and transport in streptococcus pneumoniae.
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Authors
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D.W.Abbott,
M.A.Higgins,
S.Hyrnuik,
B.Pluvinage,
A.Lammerts van bueren,
A.B.Boraston.
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Ref.
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Mol Microbiol, 2010,
77,
183-199.
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PubMed id
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Abstract
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SUMMARY The genome of Streptococcus pneumoniae strains, as typified by the TIGR4
strain, contains several genes encoding proteins putatively involved in
alpha-glucan degradation, modification and synthesis. The extracellular
components comprise an ABC-transporter with its solute-binding protein, MalX,
and the hydrolytic enzyme SpuA. We show that of the commonly occurring exogenous
alpha-glucans, S. pneumoniae TIGR4 is only able to grow on glycogen in a MalX
and SpuA-dependent manner. SpuA is able to degrade glycogen into a ladder of
alpha-1,4-glucooligosaccharides while the high affinity interaction (K(a)
approximately 10(6) M(-1)) of MalX with maltooligosaccharides plays a key role
in promoting the selective uptake of the glycogen degradation products that are
produced by SpuA. The X-ray crystallographic analyses of apo- and complexed MalX
illuminate the protein's specificity for the degradation products of glycogen
and its striking ability to recognize the helical structure of the ligand.
Overall, the results of this work provide new structural and functional insight
into streptococcal alpha-glucan metabolism while supplying biochemical support
for the hypothesis that the substrate of the S. pneumoniaealpha-glucan
metabolizing machinery is glycogen, which in a human host is abundant in lung
epithelial cells, a common target for invasive S. pneumoniae.
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