Structural highlights
Function
SECBL_MYCTU Chaperone component of an atypical, type II toxin-antitoxin chaperone (TAC) system. Prevents antitoxin HigA1 aggregation in vitro at a 1:3 chaperone:antitoxin ratio, probably also protects antitoxin HigA1 from protease. Required for neutralization of toxin HigB1 upon ectopic expression in Mycobacterium marinum or E.coli. When expressed in E.coli complements a secB deletion, restores export of OmpA and MBP and inhibits aggregation of proOmpC although it is less efficient than endogenous SecB. Complements the general chaperone function of E.coli SecB less well.[1]
Publication Abstract from PubMed
SecB chaperones assist protein export by binding both unfolded proteins and the SecA motor. Certain SecB homologs can also control toxin-antitoxin (TA) systems known to modulate bacterial growth in response to stress. In such TA-chaperone (TAC) systems, SecB assists the folding and prevents degradation of the antitoxin, thus facilitating toxin inhibition. Chaperone dependency is conferred by a C-terminal extension in the antitoxin known as chaperone addiction (ChAD) sequence, which makes the antitoxin aggregation-prone and prevents toxin inhibition. Using TAC of Mycobacterium tuberculosis, we present the structure of a SecB-like chaperone bound to its ChAD peptide. We find differences in the binding interfaces when compared to SecB-SecA or SecB-preprotein complexes, and show that the antitoxin can reach a functional form while bound to the chaperone. This work reveals how chaperones can use discrete surface binding regions to accommodate different clients or partners and thereby expand their substrate repertoire and functions.
Structural insights into chaperone addiction of toxin-antitoxin systems.,Guillet V, Bordes P, Bon C, Marcoux J, Gervais V, Sala AJ, Dos Reis S, Slama N, Mares-Mejia I, Cirinesi AM, Maveyraud L, Genevaux P, Mourey L Nat Commun. 2019 Feb 15;10(1):782. doi: 10.1038/s41467-019-08747-4. PMID:30770830[2]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Bordes P, Cirinesi AM, Ummels R, Sala A, Sakr S, Bitter W, Genevaux P. SecB-like chaperone controls a toxin-antitoxin stress-responsive system in Mycobacterium tuberculosis. Proc Natl Acad Sci U S A. 2011 May 17;108(20):8438-43. doi:, 10.1073/pnas.1101189108. Epub 2011 May 2. PMID:21536872 doi:http://dx.doi.org/10.1073/pnas.1101189108
- ↑ Guillet V, Bordes P, Bon C, Marcoux J, Gervais V, Sala AJ, Dos Reis S, Slama N, Mares-Mejia I, Cirinesi AM, Maveyraud L, Genevaux P, Mourey L. Structural insights into chaperone addiction of toxin-antitoxin systems. Nat Commun. 2019 Feb 15;10(1):782. doi: 10.1038/s41467-019-08747-4. PMID:30770830 doi:http://dx.doi.org/10.1038/s41467-019-08747-4
