EsxA has long been recognized as an important virulence factor of Mycobacterium tuberculosis (Mtb) that plays an essential role in Mtb cytosolic translocation presumably by penetrating phagosomal membranes with its acidic pH-dependent membrane permeabilizing activity (MPA). However, current data suggest that the observed cytolytic activity of EsxA at neutral pH is due to contamination of ASB-14, a detergent used in EsxA protein purification, and the role of EsxA MPA in Mtb cytosolic translocation is also questionable. Here, we have obtained evidence that it is ASB-14, not EsxA that causes cytolysis at neutral pH. Quantitative liquid chromatography and mass spectrometry showed that even after gel filtration, dialysis, or passing through detergent removal column, the remaining ASB-14 in the EsxA protein solution was still at a concentration enough to kill cultured lung epithelial cells. When treated with trypsin or proteinase K, the digested EsxA protein solution with ASB-14 was still cytotoxic. Interestingly, however, we have found that the exogenously added EsxA is endocytosed into lung epithelial cells and inserts into the host membranes within acidic subcellular compartments, which can be blocked by cytochalasin D and bafilomycin A. It is for the first time EsxA is found to insert into the host membranes within acidic subcellular compartments. ### Competing Interest Statement
- Downloaded 200 times
- Download rankings, all-time:
- Site-wide: 115,127
- In biochemistry: 3,422
- Year to date:
- Site-wide: 73,193
- Since beginning of last month:
- Site-wide: 39,504
Downloads over time
Distribution of downloads per paper, site-wide
- 27 Nov 2020: The website and API now include results pulled from medRxiv as well as bioRxiv.
- 18 Dec 2019: We're pleased to announce PanLingua, a new tool that enables you to search for machine-translated bioRxiv preprints using more than 100 different languages.
- 21 May 2019: PLOS Biology has published a community page about Rxivist.org and its design.
- 10 May 2019: The paper analyzing the Rxivist dataset has been published at eLife.
- 1 Mar 2019: We now have summary statistics about bioRxiv downloads and submissions.
- 8 Feb 2019: Data from Altmetric is now available on the Rxivist details page for every preprint. Look for the "donut" under the download metrics.
- 30 Jan 2019: preLights has featured the Rxivist preprint and written about our findings.
- 22 Jan 2019: Nature just published an article about Rxivist and our data.
- 13 Jan 2019: The Rxivist preprint is live!