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ABC Transporters: Exporter

ABC Transporters: Exporter

ATP-binding cassette or ABC transporter is the largest superfamily of integral membrane proteins. The transporters have transmembrane-binding domains (TMDs) and nucleotide-binding domains (NBDs). The TMDs are specific to their substrates, whereas the NBDs are similar to engines that complete ATP hydrolysis to complete the substrate transport. They can be full transporters consisting of two TMDs and NBDs, half transporters with one TMD and NBD, while some encoded with a single TMD or NBD are...

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Related Experiment Video

Updated: Jun 12, 2026

Monitoring the Assembly of a Secreted Bacterial Virulence Factor Using Site-specific Crosslinking

Monitoring the Assembly of a Secreted Bacterial Virulence Factor Using Site-specific Crosslinking

Published on: December 17, 2013

The autoinducer-2 exporter superfamily.

Rachael E Rettner¹, Milton H Saier

¹Division of Biological Sciences, University of California at San Diego, La Jolla, CA 92093-0116, USA.

Journal of Molecular Microbiology and Biotechnology

|June 19, 2010

Summary

The TqsA protein exports the unique autoinducer-2 (AI-2) molecule. This study characterizes the AI-2 exporter (AI-2E) superfamily, revealing their bacterial origins and evolutionary duplication events.

Area of Science:

Microbiology
Structural Biology
Biochemistry

Background:

The TqsA (YdgG) protein from Escherichia coli is known to export autoinducer-2 (AI-2), a unique furanosyl borate diester.
TqsA is part of the AI-2 exporter (AI-2E) superfamily, a group of bacterial transporters with no other functionally characterized members.

Purpose of the Study:

To characterize the AI-2 exporter (AI-2E) superfamily of bacterial transporters.
To investigate the evolutionary origins and structural features of these proteins.

Main Methods:

Bioinformatic analysis of conserved residues and motifs.
Comparative sequence analysis to infer evolutionary history.
Structural topology prediction.

Main Results:

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AI-2E proteins are exclusively bacterial, found across diverse kingdoms.
These transporters possess a conserved 8-transmembrane segment topology, likely evolved from a 4-TMS precursor via duplication.
Sequence diversity suggests functional specialization between the N-terminal and C-terminal halves.
Conserved residues and motifs were identified, and some homologues contain additional catalytic domains.

Conclusions:

The AI-2E superfamily represents a unique class of bacterial transporters with a distinct evolutionary trajectory.
Understanding the structure-function relationships within this superfamily can guide future research into AI-2 transport and bacterial communication.