Affiliation:
1. Microbiology, King's College London Dental Institute, London, United Kingdom
Abstract
ABSTRACT
Streptococcus mutans
has a significant number of transporters of the ATP-binding cassette (ABC) superfamily. Members of this superfamily are involved in the translocation of a diverse range of molecules across membranes. However, the functions of many of these members remain unknown. We have investigated the role of the single
S. mutans
representative of the second subfamily of carbohydrate uptake transporters (CUT2) of the ABC superfamily. The genetic context of genes encoding this transporter indicates that it may have a role in ribonucleoside scavenging. Inactivation of
rnsA
(ATPase) or
rnsB
(solute binding protein) resulted in strains resistant to 5-fluorocytidine and 5-fluorouridine (toxic ribonucleoside analogues). As other ribonucleosides including cytidine, uridine, adenosine, 2-deoxyuridine, and 2-deoxycytidine protected
S. mutans
from 5-fluorocytidine and 5-fluorouridine toxicity, it is likely that this transporter is involved in the uptake of these molecules. Indeed, the
rnsA
and
rnsB
mutants were unable to transport [2-
14
C]cytidine or [2-
14
C]uridine and had significantly reduced [8-
14
C]adenosine uptake rates. Characterization of this transporter in wild-type
S. mutans
indicates that it is a high-affinity (
K
m
= 1 to 2 μM) transporter of cytidine, uridine, and adenosine. The inhibition of [
14
C]cytidine uptake by a range of structurally related molecules indicates that the CUT2 transporter is involved in the uptake of most ribonucleosides, including 2-deoxyribonucleosides, but not ribose or nucleobases. The characterization of this permease has directly shown for the first time that an ABC transporter is involved in the uptake of ribonucleosides and extends the range of substrates known to be transported by members of the ABC transporter superfamily.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
23 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献