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== Publication Abstract from PubMed ==

Type-1 secretion systems (T1SSs) represent a widespread mode of protein secretion across the cell envelope in Gram-negative bacteria. The T1SS is composed of an inner-membrane ABC transporter, a periplasmic membrane-fusion protein, and an outer-membrane porin. These three components assemble into a complex spanning both membranes and providing a conduit for the translocation of unfolded polypeptides. We show that ATP hydrolysis and assembly of the entire T1SS complex is necessary for protein secretion. Furthermore, we present a 3.15-A crystal structure of AaPrtD, the ABC transporter found in the Aquifex aeolicus T1SS. The structure suggests a substrate entry window just above the transporter's nucleotide binding domains. In addition, highly kinked transmembrane helices, which frame a narrow channel not observed in canonical peptide transporters, are likely involved in substrate translocation. Overall, the AaPrtD structure supports a polypeptide transport mechanism distinct from alternating access.

Structure of a Type-1 Secretion System ABC Transporter.,Morgan JL, Acheson JF, Zimmer J Structure. 2017 Mar 7;25(3):522-529. doi: 10.1016/j.str.2017.01.010. Epub 2017, Feb 16. PMID:28216041<ref>PMID:28216041</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

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== References ==

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