6f3z
Complex of E. coli LolA and periplasmic domain of LolC
Structural highlights
Function[LOLC_ECOLI] Part of an ATP-dependent transport system LolCDE responsible for the release of lipoproteins targeted to the outer membrane from the inner membrane. Such a release is dependent of the sorting-signal (absence of an Asp at position 2 of the mature lipoprotein) and of LolA. [LOLA_ECOLI] Participates in the translocation of lipoproteins from the inner membrane to the outer membrane. Only forms a complex with a lipoprotein if the residue after the N-terminal Cys is not an aspartate (The Asp acts as a targeting signal to indicate that the lipoprotein should stay in the inner membrane); the inner membrane retention signal functions at the release step.[1] May act as a regulator of the RCS-phosphorelay signal transduction pathway.[2] Publication Abstract from PubMedIn Gram-negative bacteria, outer-membrane lipoproteins are essential for maintaining cellular integrity, transporting nutrients, establishing infections, and promoting the formation of biofilms. The LolCDE ABC transporter, LolA chaperone, and LolB outer-membrane receptor form an essential system for transporting newly matured lipoproteins from the outer leaflet of the cytoplasmic membrane to the innermost leaflet of the outer membrane. Here, we present a crystal structure of LolA in complex with the periplasmic domain of LolC. The structure reveals how a solvent-exposed beta-hairpin loop (termed the "Hook") and trio of surface residues (the "Pad") of LolC are essential for recruiting LolA from the periplasm and priming it to receive lipoproteins. Experiments with purified LolCDE complex demonstrate that association with LolA is independent of nucleotide binding and hydrolysis, and homology models based on the MacB ABC transporter predict that LolA recruitment takes place at a periplasmic site located at least 50 A from the inner membrane. Implications for the mechanism of lipoprotein extraction and transfer are discussed. The LolA-LolC structure provides atomic details on a key protein interaction within the Lol pathway and constitutes a vital step toward the complete molecular understanding of this important system. Insights into bacterial lipoprotein trafficking from a structure of LolA bound to the LolC periplasmic domain.,Kaplan E, Greene NP, Crow A, Koronakis V Proc Natl Acad Sci U S A. 2018 Jul 16. pii: 1806822115. doi:, 10.1073/pnas.1806822115. PMID:30012603[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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