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Published online: 27 January 2010 | doi:10.1038/nchina.2010.9
Structural biology: Finding the way in
Felix Cheung
Abstract
High-resolution crystal structure analysis reveals how the amino acid antiporter of Escherichia coli recognizes and transports extracellular arginine
Original article citation
et al. Mechanism of substrate recognition and transport by an amino acid antiporter. Nature doi:10.1038/nature08741 (2010).Introduction
© (2010) Nature
Escherichia coli can survive the extremely acidic environment of the stomach because its plasma membrane contains AdiC, an amino acid antiporter that expels protons from the cytoplasm to the periplasm through the exchange of intracellular agmatine (Agm) and extracellular arginine (Arg). Yigong Shi and co-workers at Tsinghua University in Beijing1 have recently determined the crystal structure of AdiC (see Structural biology: The amino acid antiporter). Now, they have found the mechanism2 by which AdiC recognizes and transports Arg.
The AdiC homodimer is assembled from two asymmetric units, each containing 12 transmembrane segments. In its default 'substrate-free' state, AdiC has an open, periplasm-facing cavity in which extracellular Arg is believed to be bound.
The researchers resolved the crystal structure of an E. coli AdiC variant bound to Arg (see image; Arg is circled in green). The positively charged Arg is enclosed in an acidic binding chamber, with the head groups of Arg located near the four oxygen atoms in AdiC and the aliphatic portion of Arg located near the hydrophobic chains of three highly conserved amino acids.
In contrast to the open conformation of the default state, the Arg-bound AdiC has a closed conformation. Structural analysis identified three potential gates that may work in concert to differentially regulate the upload and release of Arg and Agm.
The authors of this work are from:
Protein Science Laboratory, Ministry of Education, Tsinghua University, Beijing, China; State Key Laboratory of Biomembrane and Membrane Biotechnology, Center for Structural Biology, School of Life Sciences and School of Medicine, Tsinghua University, Beijing, China; School of Life Sciences, Shandong University, Jinan, Shandong, China.
References
- Gao, X. et al. Structure and mechanism of an amino acid antiporter. Science 324, 1565–1568 (2009). | Article | PubMed | ADS | OpenURL | | ChemPort |
- Gao, X. et al. Mechanism of substrate recognition and transport by an amino acid antiporter. Nature doi:10.1038/nature08741 (2010). | Article | OpenURL
