TY - JOUR T1 - "Just a spoonful of sugar...": import of sialic acid across bacterial cell membranes. JF - Biophys Rev Y1 - 2018 A1 - North, Rachel A A1 - Horne, Christopher R A1 - Davies, James S A1 - Remus, Daniela M A1 - Muscroft-Taylor, Andrew C A1 - Goyal, Parveen A1 - Wahlgren, Weixiao Yuan A1 - Ramaswamy, S A1 - Friemann, Rosmarie A1 - Dobson, Renwick C J AB -

Eukaryotic cell surfaces are decorated with a complex array of glycoconjugates that are usually capped with sialic acids, a large family of over 50 structurally distinct nine-carbon amino sugars, the most common member of which is N-acetylneuraminic acid. Once made available through the action of neuraminidases, bacterial pathogens and commensals utilise host-derived sialic acid by degrading it for energy or repurposing the sialic acid onto their own cell surface to camouflage the bacterium from the immune system. A functional sialic acid transporter has been shown to be essential for the uptake of sialic acid in a range of human bacterial pathogens and important for host colonisation and persistence. Here, we review the state-of-play in the field with respect to the molecular mechanisms by which these bio-nanomachines transport sialic acids across bacterial cell membranes.

VL - 10 IS - 2 ER - TY - JOUR T1 - Substrate-bound outward-open structure of a Na-coupled sialic acid symporter reveals a new Na site. JF - Nat Commun Y1 - 2018 A1 - Wahlgren, Weixiao Y A1 - Dunevall, Elin A1 - North, Rachel A A1 - Paz, Aviv A1 - Scalise, Mariafrancesca A1 - Bisignano, Paola A1 - Bengtsson-Palme, Johan A1 - Goyal, Parveen A1 - Claesson, Elin A1 - Caing-Carlsson, Rhawnie A1 - Andersson, Rebecka A1 - Beis, Konstantinos A1 - Nilsson, Ulf J A1 - Farewell, Anne A1 - Pochini, Lorena A1 - Indiveri, Cesare A1 - Grabe, Michael A1 - Dobson, Renwick C J A1 - Abramson, Jeff A1 - Ramaswamy, S A1 - Friemann, Rosmarie AB -

Many pathogenic bacteria utilise sialic acids as an energy source or use them as an external coating to evade immune detection. As such, bacteria that colonise sialylated environments deploy specific transporters to mediate import of scavenged sialic acids. Here, we report a substrate-bound 1.95 Å resolution structure and subsequent characterisation of SiaT, a sialic acid transporter from Proteus mirabilis. SiaT is a secondary active transporter of the sodium solute symporter (SSS) family, which use Na gradients to drive the uptake of extracellular substrates. SiaT adopts the LeuT-fold and is in an outward-open conformation in complex with the sialic acid N-acetylneuraminic acid and two Na ions. One Na binds to the conserved Na2 site, while the second Na binds to a new position, termed Na3, which is conserved in many SSS family members. Functional and molecular dynamics studies validate the substrate-binding site and demonstrate that both Na sites regulate N-acetylneuraminic acid transport.

VL - 9 IS - 1 ER - TY - JOUR T1 - Crystal structure of N-acetylmannosamine kinase from Fusobacterium nucleatum. JF - Acta Crystallogr F Struct Biol Commun Y1 - 2017 A1 - Caing-Carlsson, Rhawnie A1 - Goyal, Parveen A1 - Sharma, Amit A1 - Ghosh, Swagatha A1 - Setty, Thanuja Gangi A1 - North, Rachel A A1 - Friemann, Rosmarie A1 - Ramaswamy, S KW - Adenosine Triphosphate KW - Amino Acid Sequence KW - Bacterial Proteins KW - Binding Sites KW - Cloning, Molecular KW - Crystallography, X-Ray KW - Escherichia coli KW - Fusobacterium nucleatum KW - Gene Expression KW - Genetic Vectors KW - Hexosamines KW - Models, Molecular KW - Phosphotransferases (Alcohol Group Acceptor) KW - Protein Binding KW - Protein Conformation, alpha-Helical KW - Protein Conformation, beta-Strand KW - Protein Interaction Domains and Motifs KW - Protein Multimerization KW - Recombinant Proteins KW - Sequence Alignment KW - Sequence Homology, Amino Acid KW - Substrate Specificity AB -

Sialic acids comprise a varied group of nine-carbon amino sugars that are widely distributed among mammals and higher metazoans. Some human commensals and bacterial pathogens can scavenge sialic acids from their environment and degrade them for use as a carbon and nitrogen source. The enzyme N-acetylmannosamine kinase (NanK; EC 2.7.1.60) belongs to the transcriptional repressors, uncharacterized open reading frames and sugar kinases (ROK) superfamily. NanK catalyzes the second step of the sialic acid catabolic pathway, transferring a phosphate group from adenosine 5'-triphosphate to the C6 position of N-acetylmannosamine to generate N-acetylmannosamine 6-phosphate. The structure of NanK from Fusobacterium nucleatum was determined to 2.23 Å resolution by X-ray crystallography. Unlike other NanK enzymes and ROK family members, F. nucleatum NanK does not have a conserved zinc-binding site. In spite of the absence of the zinc-binding site, all of the major structural features of enzymatic activity are conserved.

VL - 73 IS - Pt 6 ER -