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The MgtE family of Mg2+ transporters is ubiquitously conserved in all domains of life. The cytosolic domains of the MgtE Mg2+ transporters include a cystathionine-β-synthase (CBS) domain which is known to play a regulatory function in transporter proteins. The cytosolic domain of MgtE from Thermus thermophilus was overexpressed, purified and crystallized in the presence and absence of Mg2+. The crystals formed in the presence of Mg2+ diffracted X-rays to 2.3 Å resolution using synchrotron radiation, belong to space group P6522 with unit-cell parameters a = b = 57.7, c = 317.6 Å and are expected to contain one molecule in the asymmetric unit. The crystals formed in the absence of Mg2+ diffracted X-rays to 3.5 Å resolution using synchrotron radiation, belong to space group P212121 with unit-cell parameters a = 77.0, b = 100.3, c = 100.3 Å and are expected to contain two molecules in the asymmetric unit. [ABSTRACT FROM AUTHOR]

The cation diffusion facilitator (CDF) family proteins are ubiquitously distributed in the three domains of life and transport metals such as zinc and various heavy metals. Prokaryotic CDF proteins consists of an N-terminal putative six-transmembrane domain followed by a C-terminal cytosolic domain. The cytosolic domain of the CDF-family protein from Thermotoga maritima has been overexpressed, purified and crystallized. The selenomethionine-substituted crystals diffracted X-rays to 2.5 Å resolution using synchrotron radiation, belonged to space group R32, with unit-cell parameters a = b = 97.7, c = 83.4 Å, and are expected to contain one molecule in each asymmetric unit. [ABSTRACT FROM AUTHOR]

The MgtE family of Mg2+ transporters are ubiquitously conserved in all three domains. The genes encoding full-length MgtE from seven different species were cloned. Three of the seven MgtE transporters were overexpressed and purified for use in crystallization trials. Only Thermus thermophilus MgtE was successfully crystallized using the sitting-drop vapour-diffusion method. Selenomethionine-substituted (SeMet) crystals were obtained by cross-microseeding using the native microcrystals. The SeMet crystals diffracted X-rays to 3.5 Å resolution using synchrotron radiation and belong to space group C2221, with unit-cell parameters a = 118.3, b = 134.9, c = 366.2 Å. Structure determination is in progress. [ABSTRACT FROM AUTHOR]

Summary The multidrug and toxic compound extrusion (MATE) family of proteins consists of transporters responsible for multidrug resistance in prokaryotes. In plants, a number of MATE proteins were identified by recent genomic and functional studies, which imply that the proteins have substrate-specific transport functions instead of multidrug extrusion. The three-dimensional structure of eukaryotic MATE proteins, including those of plants, has not been reported, preventing a better understanding of the molecular mechanism of these proteins. Here, we describe the crystal structure of a MATE protein from the plant Camelina sativa at 2.9 Å resolution. Two sets of six transmembrane α helices, assembled pseudo-symmetrically, possess a negatively charged internal pocket with an outward-facing shape. The crystal structure provides insight into the diversity of plant MATE proteins and their substrate recognition and transport through the membrane. [ABSTRACT FROM AUTHOR]

The bacterial peptidoglycan enclosing the cytoplasmic membrane is a fundamental cellular architecture. The integral membrane protein MurJ plays an essential role in flipping the cell wall building block Lipid II across the cytoplasmic membrane for peptidoglycan biosynthesis. Previously reported crystal structures of MurJ have elucidated its V-shaped inward- or outward-facing forms with an internal cavity for substrate binding. MurJ transports Lipid II using its cavity through conformational transitions between these two forms. Here, we report two crystal structures of inward-facing forms from Arsenophonus endosymbiont MurJ and an unprecedented crystal structure of Escherichia coli MurJ in a "squeezed" form, which lacks a cavity to accommodate the substrate, mainly because of the increased proximity of transmembrane helices 2 and 8. Subsequent molecular dynamics simulations supported the hypothesis that the squeezed form is an intermediate conformation. This study fills a gap in our understanding of the Lipid II flipping mechanism. [Display omitted] • Crystal structures of bacterial MurJ reveal its squeezed and inward forms • The squeezed form does not contain an internal cavity required for substrate binding • Transmembrane helices 2, 7, and 8 contribute to MurJ structural transitions • The squeezed form occurs during outward-to-inward conformational changes Kohga et al. present an unprecedented "squeezed" structure of MurJ, a Lipid II flippase that is essential for peptidoglycan biogenesis in gram-negative bacteria. The "squeezed" form is proposed to be an intermediate during outward-to-inward conformational changes after substrate release, which is further supported by molecular dynamics simulations. [ABSTRACT FROM AUTHOR]