Structural highlights
FunctionHLYB_ECOL6 Part of the ABC transporter complex HlyBD involved in hemolysin export. Transmembrane domains (TMD) form a pore in the inner membrane and the ATP-binding domain (NBD) is responsible for energy generation (By similarity). Publication Abstract from PubMedType 1 secretion systems (T1SSs) are widespread in pathogenic Gram-negative bacteria, extruding protein substrates following synthesis of the entire polypeptide. The Escherichia coli hemolysin A secretion system has long been considered a prototype in structural and mechanistic studies of T1SSs. Three membrane proteins-an inner membrane ABC transporter HlyB, an adaptor protein HlyD, and an outer membrane porin TolC-are required for secretion. However, the stoichiometry and structure of the complex are unknown. Here, cryo-electron microscopy (cryo-EM) structures determined in two conformations reveal that the inner membrane complex is a hetero-dodecameric assembly comprising three HlyB homodimers and six HlyD subunits. Functional studies indicate that oligomerization of HlyB and HlyD is essential for protein secretion and that polypeptides translocate through a canonical ABC transporter pathway in HlyB. Our data suggest that T1SSs entail three ABC transporters, one that functions as a protein channel and two that allosterically power the translocation process. The hemolysin A secretion system is a multi-engine pump containing three ABC transporters.,Zhao H, Lee J, Chen J Cell. 2022 Sep 1;185(18):3329-3340.e13. doi: 10.1016/j.cell.2022.07.017. PMID:36055198[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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