Purine substrate recognition by the nucleobase-ascorbate transporter signature motif in the YgfO xanthine permease: ASN-325 binds and ALA-323 senses substrate.

ABSTRACT: The nucleobase-ascorbate transporter (NAT) signature motif is a conserved 11-amino acid sequence of the ubiquitous NAT/NCS2 family, essential for function and selectivity of both a bacterial (YgfO) and a fungal (UapA) purine-transporting homolog. We examined the role of NAT motif in more detail, using Cys-scanning and site-directed alkylation analysis of the YgfO xanthine permease of Escherichia coli. Analysis of single-Cys mutants in the sequence 315-339 for sensitivity to inactivation by 2-sulfonatoethyl methanethiosulfonate (MTSES(-)) and N-ethylmaleimide (NEM) showed a similar pattern: highly sensitive mutants clustering at the motif sequence (323-329) and a short alpha-helical face downstream (332, 333, 336). In the presence of substrate, N325C is protected from alkylation with either

SUBMITTER: Georgopoulou E 

PROVIDER: S-EPMC2885222 | biostudies-literature | 2010 Jun

REPOSITORIES: biostudies-literature