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The molecular basis of glycogen breakdown and transport in Streptococcus pneumoniae
Author(s) -
Abbott D. Wade,
Higgins Melanie A.,
Hyrnuik Susanne,
Pluvinage Benjamin,
Lammerts van Bueren Alicia,
Boraston Alisdair B.
Publication year - 2010
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2010.07199.x
Subject(s) - biology , streptococcus pneumoniae , glycogen , biochemistry , glucan , polysaccharide , atp binding cassette transporter , glycogen synthase , transporter , gene , antibiotics
Summary The genome of Streptococcus pneumoniae strains, as typified by the TIGR4 strain, contain several genes encoding proteins putatively involved in α‐glucan degradation, modification and synthesis. The extracellular components comprise an ATP binding cassette‐transporter with its solute binding protein, MalX, and the hydrolytic enzyme SpuA. We show that of the commonly occurring exogenous α‐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 α‐1,4‐glucooligosaccharides while the high‐affinity interaction ( K a ∼ 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 α‐glucan metabolism while supplying biochemical support for the hypothesis that the substrate of the S. pneumoniae α‐glucan metabolizing machinery is glycogen, which in a human host is abundant in lung epithelial cells, a common target for invasive S. pneumoniae .