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Figure 4
The tentative working mode of dimeric abMltA on the bacterial outer membrane. (a) Cartoon representation of abMltA colored according to the degree of amino-acid sequence conservation as analyzed by the ConSurf server. The side chains of completely conserved residues are shown with a ball-shaped model (lower panel) for better visualization. (b) Sequence alignment of MltA between different species. Mostly conserved and partially conserved residues are colored red and blue, respectively. The positions of the extra domain are highlighted by a green box. * indicates conserved residues that are involved in substrate binding. # indicates the conserved cysteine residue at the N-terminus of MltA, which is modified by lipid attachment for membrane anchoring. (c) Structural superposition of abMltA with the ecMltA–substrate complex. Seven residues that are involved in substrate recognition are labeled. The most critical residue directly involved in the cleavage of the substrate, Asp328 in ecMltA and Asp354 in abMltA, is highlighted using a red box. (d) Tentative working model of dimeric abMltA on the bacterial outer membrane. Red balls indicate the location of Asp354 (Asp328 in ecMltA), which is the most critical residue for the activity of MltA. OM and IM indicate the outer and inner membranes, respectively.

IUCrJ
Volume 8| Part 6| November 2021| Pages 921-930
ISSN: 2052-2525
https://doi.org/10.1107/S2052252521008666