INF2 mutations appear to cause many cases of FSGS-associated Charcot-Marie-Tooth neuropathy, showing that INF2 is involved in a disease affecting both the kidney glomerulus and the peripheral nervous system. These findings provide new insights into the pathophysiological mechanisms linking formin proteins to podocyte and Schwann-cell function. (Funded by the Agence Nationale de la Recherche and others.).

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OprM and OprN belong to the outer membrane factor family proteins. These approximately 52 kDa proteins are part of the tripartite efflux pumps found in Pseudomonas aeruginosa and are responsible in part for the antibiotic resistance observed in these bacteria. Both proteins have been expressed in Escherichia coli as His-tag proteins and purified accordingly by affinity chromatography in the presence of n-octyl-beta-D-glucopyranoside detergent. OprM and OprN were crystallized using PEG 20 000/ammonium citrate and ammonium sulfate as precipitating agents, respectively. Crystals belong to space group C2, with unit-cell parameters a = 152.6, b = 87.9, c = 355.9 A, beta = 98.9 degrees and a = 151.3, b = 87.6, c = 356.5 A, beta = 98.1 degrees for OprM and OprN, respectively. Using the ESRF synchrotron-radiation source, OprM diffraction data extended to 3.4 A.

One of the major families of membrane proteins found in prokaryote genome corresponds to the transporters. Among them, the resistance-nodulation-cell division (RND) transporters are highly studied, as being responsible for one of the most problematic mechanisms used by bacteria to resist to antibiotics, i.e., the active efflux of drugs. In Gram-negative bacteria, these proteins are inserted in the inner membrane and form a tripartite assembly with an outer membrane factor and a periplasmic linker in order to cross the two membranes to expulse molecules outside of the cell. A lot of information has been collected to understand the functional mechanism of these pumps, especially with AcrAB-TolC from Escherichia coli, but one missing piece from all the suggested models is the role of peptidoglycan in the assembly. Here, by pull-down experiments with purified peptidoglycans, we precise the MexAB-OprM interaction with the peptidoglycan from Escherichia coli and Pseudomonas aeruginosa, highlighting a role of the peptidoglycan in stabilizing the MexA-OprM complex and also differences between the two Gram-negative bacteria peptidoglycans.