Accessibility from the Cytoplasm Is Critical for ssrA Tag-Mediated Degradation of Integral Membrane Proteins by ClpXP Protease

Thilini Abeywansha, Qian Chai, Xinyi Zhang, Zhaoshuai Wang, Yinan Wei

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


The AAA+ protease ClpXP has long been established as the cellular rescue system that degrades ssrA-tagged proteins resulting from stalled ribosomes. Until recently, in all of these studies soluble proteins were used as model substrates, since the ClpXP complex and the related adapter SspB are all cytosolic proteins. In a previous study, we found that the introduction of an ssrA tag can facilitate complete degradation of a large and stable trimeric integral membrane protein AcrB, which is the first reported example of a membrane protein substrate. To investigate the mechanism of degradation of a membrane protein by a soluble protein complex, we experimented with the truncation of the C-terminal tail of AcrB. We found that the C-terminal tail is important for degradation, as systematic truncation of the tail diminished degradation. Thus, we hypothesize that membrane proteins need a cytosolic tail/domain for ClpXP-SspB to latch on to initiate degradation. To test this hypothesis, we introduced the ssrA tag at the C-terminal of several membrane proteins, including AqpZ, YiiP, YajR, as well as their truncation fragments, and examined their degradation. We found that the ssrA-facilitated degradation of membrane proteins by ClpXP-SspB depends on the presence of a CT tail or domain, which is critical for accessibility of the tag by ClpXP-SspB. When the ssrA tag is not well-exposed to the cytosol, FtsH can access and degrade the tagged protein, given that the substrate protein is metastable.

Original languageEnglish
Pages (from-to)5602-5608
Number of pages7
Issue number38
StatePublished - Sep 25 2018

Bibliographical note

Funding Information:
This study is supported by the NSF grant CHE-1709381 to Y.W.

Publisher Copyright:
Copyright © 2018 American Chemical Society.

ASJC Scopus subject areas

  • Biochemistry


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