Header

UZH-Logo

Maintenance Infos

Asymmetry in the homodimeric ABC transporter MsbA recognized by a DARPin


Mittal, Anshumali; Böhm, Simon; Grütter, Markus G; Bordignon, Enrica; Seeger, Markus A (2012). Asymmetry in the homodimeric ABC transporter MsbA recognized by a DARPin. Journal of Biological Chemistry, 287(24):20395-20406.

Abstract

ABC transporters harness the energy from ATP binding and hydrolysis to translocate substrates across the membrane. Binding of two ATP molecules at the nucleotide binding domains (NBDs) leads to the formation of an outward-facing state. The conformational changes required to reset the transporter to the inward-facing state are initiated by sequential hydrolysis of the bound nucleotides. In a homodimeric ABC exporter such as MsbA responsible for lipid A transport in Escherichia coli, sequential ATP hydrolysis implies the existence of an asymmetric conformation. Here we report the in vitro selection of a designed ankyrin repeat protein (DARPin) specifically binding to detergent-solubilized MsbA. Only one DARPin binds to the homodimeric transporter in the absence as well as in the presence of nucleotides, suggesting that it recognizes asymmetries in MsbA. DARPin binding increases the rate of ATP hydrolysis by a factor of two independent of the substrate-induced ATPase stimulation. Electron paramagnetic resonance (EPR) measurements are found to be in good agreement with the available crystal structures and reveal that DARPin binding does not affect the large nucleotide-driven conformational changes of MsbA. The binding epitope was mapped by cross-linking and EPR to the membrane-spanning part of the transmembrane domain (TMD). Using cross-linked DARPin-MsbA complexes, 8-azido-ATP was found to preferentially photolabel one chain of the homodimer, suggesting that the asymmetries captured by DARPin binding at the TMDs are propagated to the NBDs. This work demonstrates that in vitro selected binders are useful tools to study the mechanism of membrane proteins.

Abstract

ABC transporters harness the energy from ATP binding and hydrolysis to translocate substrates across the membrane. Binding of two ATP molecules at the nucleotide binding domains (NBDs) leads to the formation of an outward-facing state. The conformational changes required to reset the transporter to the inward-facing state are initiated by sequential hydrolysis of the bound nucleotides. In a homodimeric ABC exporter such as MsbA responsible for lipid A transport in Escherichia coli, sequential ATP hydrolysis implies the existence of an asymmetric conformation. Here we report the in vitro selection of a designed ankyrin repeat protein (DARPin) specifically binding to detergent-solubilized MsbA. Only one DARPin binds to the homodimeric transporter in the absence as well as in the presence of nucleotides, suggesting that it recognizes asymmetries in MsbA. DARPin binding increases the rate of ATP hydrolysis by a factor of two independent of the substrate-induced ATPase stimulation. Electron paramagnetic resonance (EPR) measurements are found to be in good agreement with the available crystal structures and reveal that DARPin binding does not affect the large nucleotide-driven conformational changes of MsbA. The binding epitope was mapped by cross-linking and EPR to the membrane-spanning part of the transmembrane domain (TMD). Using cross-linked DARPin-MsbA complexes, 8-azido-ATP was found to preferentially photolabel one chain of the homodimer, suggesting that the asymmetries captured by DARPin binding at the TMDs are propagated to the NBDs. This work demonstrates that in vitro selected binders are useful tools to study the mechanism of membrane proteins.

Statistics

Citations

22 citations in Web of Science®
22 citations in Scopus®
Google Scholar™

Altmetrics

Downloads

65 downloads since deposited on 11 Oct 2012
20 downloads since 12 months
Detailed statistics

Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Department of Biochemistry
07 Faculty of Science > Department of Biochemistry
Dewey Decimal Classification:570 Life sciences; biology
Language:English
Date:2012
Deposited On:11 Oct 2012 06:42
Last Modified:26 Aug 2016 07:32
Publisher:American Society for Biochemistry and Molecular Biology
ISSN:0021-9258
Additional Information:This research was originally published in: Mittal, Anshumali; Böhm, Simon; Grütter, Markus G; Bordignon, Enrica; Seeger, Markus A (2012). Asymmetry in the homodimeric ABC transporter MsbA recognized by a DARPin. Journal of Biological Chemistry, 287(24):20395-20406. © the American Society for Biochemistry and Molecular Biology.
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1074/jbc.M112.359794
PubMed ID:22523072

Download

Preview Icon on Download
Content: Published Version
Language: English
Filetype: PDF - Registered users only
Size: 2MB
View at publisher
Preview Icon on Download
Preview
Content: Accepted Version
Filetype: PDF
Size: 3MB

TrendTerms

TrendTerms displays relevant terms of the abstract of this publication and related documents on a map. The terms and their relations were extracted from ZORA using word statistics. Their timelines are taken from ZORA as well. The bubble size of a term is proportional to the number of documents where the term occurs. Red, orange, yellow and green colors are used for terms that occur in the current document; red indicates high interlinkedness of a term with other terms, orange, yellow and green decreasing interlinkedness. Blue is used for terms that have a relation with the terms in this document, but occur in other documents.
You can navigate and zoom the map. Mouse-hovering a term displays its timeline, clicking it yields the associated documents.

Author Collaborations