6PRG

SBP RafE in complex with stachyose

Summary for 6PRG

• Entry DOI: 10.2210/pdb6prg/pdb
• Descriptor: ABC transporter sugar-binding protein, alpha-D-galactopyranose-(1-6)-alpha-D-galactopyranose-(1-6)-[beta-D-fructofuranose-(2-1)]alpha-D-glucopyranose, CITRIC ACID, ... (5 entities in total)
• Functional Keywords: cluster d-i solute binding protein, complex, sbp, sugar binding protein
• Biological source: Streptococcus pneumoniae TIGR4
• Total number of polymer chains: 2
• Total formula weight: 94845.70

Authors

Meier, E.P.W.,Boraston, A.B. (deposition date: 2019-07-10, release date: 2019-10-02, Last modification date: 2023-10-11)

Primary citation

Hobbs, J.K.,Meier, E.P.W.,Pluvinage, B.,Mey, M.A.,Boraston, A.B.
Molecular analysis of an enigmaticStreptococcus pneumoniaevirulence factor: The raffinose-family oligosaccharide utilization system.
J.Biol.Chem., 294:17197-17208, 2019

PubMed Abstract: is an opportunistic respiratory pathogen that can spread to other body sites, including the ears, brain, and blood. The ability of this bacterium to break down, import, and metabolize a wide range of glycans is key to its virulence. Intriguingly, can utilize several plant oligosaccharides for growth , including raffinose-family oligosaccharides (RFOs, which are α-(1→6)-galactosyl extensions of sucrose). An RFO utilization locus has been identified in the pneumococcal genome; however, none of the proteins encoded by this locus have been biochemically characterized. The enigmatic ability of to utilize RFOs has recently received attention because mutations in two of the RFO locus genes have been linked to the tissue tropism of clinical pneumococcal isolates. Here, we use functional studies combined with X-ray crystallography to show that although the pneumococcal RFO locus encodes for all the machinery required for uptake and degradation of RFOs, the individual pathway components are biochemically inefficient. We also demonstrate that the initiating enzyme in this pathway, the α-galactosidase Aga (a family 36 glycoside hydrolase), can cleave α-(1→3)-linked galactose units from a linear blood group antigen. We propose that the pneumococcal RFO pathway is an evolutionary relic that is not utilized in this streptococcal species and, as such, is under no selection pressure to maintain binding affinity and/or catalytic efficiency. We speculate that the apparent contribution of RFO utilization to pneumococcal tissue tropism may, in fact, be due to the essential role the ATPase RafK plays in the transport of other carbohydrates.

PubMed: 31591266
DOI: 10.1074/jbc.RA119.010280

Experimental method

X-RAY DIFFRACTION (2.35 Å)