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Molecular interactions in ribose transport: the binding protein module symmetrically associates with the homodimeric membrane transporter
Author(s) -
Park Yongkyu,
Cho YoungJin,
Ahn Taeho,
Park Chankyu
Publication year - 1999
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/18.15.4149
Subject(s) - biology , transport protein , membrane transport protein , transporter , ribose , plasma protein binding , membrane protein , dna binding protein , binding site , biochemistry , membrane , microbiology and biotechnology , biophysics , transcription factor , gene , enzyme
The Escherichia coli high‐affinity ribose transporter is composed of the periplasmic ribose‐binding protein (RBP or RbsB), the membrane component (RbsC) and the ATP‐binding protein (RbsA). In order to dissect the molecular interactions initiating the transport process, RbsC suppressors for transport‐defective rbsB mutations were isolated. These suppressors are localized in two regions of RbsC, which are allele‐specific to N‐ or C‐terminal domain mutations of RBP, suggesting that there are two distinct regions of RbsC, each interacting with one of the two domains of RBP. To demonstrate that these two regions provide a homodimeric binding surface for RBP we constructed a dimeric rbsC in which two genes are joined tandemly from head to tail with the addition of a linker. The dimeric RbsC protein is stable and functional in growth and ribose uptake. By exploiting the allele specificity between the domain‐specific mutations and their suppressors, we generated all mutation–suppressor combinations in a single rbsB plus the dimeric rbsC genes. Their phenotypes are consistent with the proposal that the binding protein module interacts symmetrically with homodimeric RbsC. The mode of association proposed here for the ribose transport components could be extended to other ABC transporters with similar structural organizations.