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Journal of Bacteriology, February 2009, p. 754-761, Vol. 191, No. 3
0021-9193/09/$08.00+0     doi:10.1128/JB.01439-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

The MalF P2 Loop of the ATP-Binding Cassette Transporter MalFGK2 from Escherichia coli and Salmonella enterica Serovar Typhimurium Interacts with Maltose Binding Protein (MalE) throughout the Catalytic Cycle {triangledown}

Martin L. Daus, Mathias Grote, and Erwin Schneider*

Institut für Biologie, AG Bakterienphysiologie, Humboldt-Universität zu Berlin, Chausseestr. 117, D-10115 Berlin, Germany

Received 14 October 2008/ Accepted 20 November 2008

We have investigated the interaction of the uncommonly large periplasmic P2 loop of the MalF subunit of the maltose ATP-binding cassette transporter (MalFGK2) from Escherichia coli and Salmonella enterica serovar Typhimurium with maltose binding protein (MalE) by site-specific chemical cross-linking in the assembled transport complex. We focused on possible distance changes between two pairs of residues of the P2 loop and MalE during the transport cycle. The distance between MalF(S205C) and MalE(T80C) (~5 Å) remained unchanged under all conditions tested. Cross-linking did not affect the ATPase activity of the complex. The distance between MalF(T177C) and MalE(T31C) changed from ~10 Å to ~5 Å upon binding of ATP (or maltose, with a less pronounced result) and was reset to ~10 Å after hydrolysis of one ATP. A cross-link (~25 Å) between MalF(S205C) and MalE(T31C) was observed only when the transporter resided in a transition state-like conformation, as was the case after vanadate trapping or in a binding protein-independent mutant, both of which are characterized by tight binding of unliganded MalE to the transporter. Thus, we propose that the observed cross-link is indicative of catalytic intermediates of the transporter. Together, our results strengthen the notion that the MalF P2 loop plays an important role in intersubunit communication. In particular, this loop is involved in keeping MalE in close contact with the transporter. The data are discussed with respect to a crystal structure and current transport models.

* Corresponding author. Mailing address: Humboldt-Universität zu Berlin, Institut für Biologie, AG Bakterienphysiologie, Chausseestr. 117, D-10115 Berlin, Germany. Phone: 49(0)30-20938121. Fax: 49(0)30-20938126. E-mail: erwin.schneider{at}rz.hu-berlin.de

{triangledown} Published ahead of print on 1 December 2008.

Journal of Bacteriology, February 2009, p. 754-761, Vol. 191, No. 3
0021-9193/09/$08.00+0     doi:10.1128/JB.01439-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Grote, M., Polyhach, Y., Jeschke, G., Steinhoff, H.-J., Schneider, E., Bordignon, E. (2009). Transmembrane Signaling in the Maltose ABC Transporter MalFGK2-E: PERIPLASMIC MalF-P2 LOOP COMMUNICATES SUBSTRATE AVAILABILITY TO THE ATP-BOUND MalK DIMER. J. Biol. Chem. 284: 17521-17526 [Abstract] [Full Text]  


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