Linked Domain Architectures Allow for Specialization of Function in the FtsK/SpoIIIE ATPases of ESX Secretion Systems
Published Date:Jun 27 2014
Source:J Mol Biol. 2014; 427(5):1119-1132.
Amino Acid Sequence
Molecular Sequence Data
Mycobacterial Protein Secretion
Protein Structure, Tertiary
Type VII Secretion System
Pubmed Central ID:PMC4277743
Funding:DP2 0D001378/DP/NCCDPHP CDC HHS/United States
DP2 OD001378/OD/NIH HHS/United States
Howard Hughes Medical Institute/United States
Description:Among protein secretion systems, there are specialized ATPases that serve different functions such as substrate recognition, substrate unfolding, and assembly of the secretory machinery. ESX (early secretory antigen target 6 kDa secretion) protein secretion systems require FtsK/SpoIIIE family ATPases but the specific function of these ATPases is poorly understood. The ATPases of ESX secretion systems have a unique domain architecture among proteins of the FtsK/SpoIIIE family. All well-studied FtsK family ATPases to date have one ATPase domain and oligomerize to form a functional molecular machine, most commonly a hexameric ring. In contrast, the ESX ATPases have three ATPase domains, encoded either by a single gene or by two operonic genes. It is currently unknown which of the ATPase domains is catalytically functional and whether each domain plays the same or a different function. Here we focus on the ATPases of two ESX systems, the ESX-1 system of Mycobacterium tuberculosis and the yuk system of Bacillus subtilis. We show that ATP hydrolysis by the ESX ATPase is required for secretion, suggesting that this enzyme at least partly fuels protein translocation. We further show that individual ATPase domains play distinct roles in substrate translocation and complex formation. Comparing the single-chain and split ESX ATPases, we reveal differences in the requirements of these unique secretory ATPases.
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