Crystal structure of the bacterial nucleoside transporter Tsx

• Published in: The EMBO journal 2004-08, Vol.23 (16), p.3187-3195
• Main Authors: Ye, Jiqing, van den Berg, Bert
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Bacteria; Bacterial Outer Membrane Proteins - chemistry; Bacterial Outer Membrane Proteins - genetics; Bacterial Outer Membrane Proteins - metabolism; binding site; Binding Sites; BNL; CRYSTAL STRUCTURE; Crystallography, X-Ray; E coli; EMBO20; EMBO40; ENT; Escherichia coli; Escherichia coli - chemistry; Escherichia coli - genetics; Escherichia coli - metabolism; Escherichia coli Proteins - chemistry; Escherichia coli Proteins - genetics; Escherichia coli Proteins - metabolism; Eukaryotic Cells - metabolism; MATERIALS SCIENCE; Membranes; Models, Molecular; Molecular Sequence Data; Mutation - genetics; NATIONAL SYNCHROTRON LIGHT SOURCE; Nucleoside Transport Proteins - chemistry; Nucleoside Transport Proteins - genetics; Nucleoside Transport Proteins - metabolism; nucleoside transporter; NUCLEOSIDES; Nucleosides - chemistry; Nucleosides - metabolism; outer membrane protein; Protein Structure, Tertiary; Receptors, Virus - chemistry; Receptors, Virus - genetics; Receptors, Virus - metabolism; Residues; Sequence Alignment; Sugar
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1038/sj.emboj.7600330

Tsx is a nucleoside‐specific outer membrane (OM) transporter of Gram‐negative bacteria. We present crystal structures of Escherichia coli Tsx in the absence and presence of nucleosides. These structures provide a mechanism for nucleoside transport across the bacterial OM. Tsx forms a monomeric, 12‐stranded β‐barrel with a long and narrow channel spanning the outer membrane. The channel, which is shaped like a keyhole, contains several distinct nucleoside‐binding sites, two of which are well defined. The base moiety of the nucleoside is located in the narrow part of the keyhole, while the sugar occupies the wider opening. Pairs of aromatic residues and flanking ionizable residues are involved in nucleoside binding. Nucleoside transport presumably occurs by diffusion from one binding site to the next.