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Ammonium transporters (Amts) are integral membrane proteins found in all kingdoms of life that fulfill an essential function in the uptake of reduced nitrogen for biosynthetic purposes. Amt-1 is one of three Amts encoded in the genome of the hyperthermophilic archaeon Archaeoglobus fulgidus. The crystal structure of Amt-1 shows a compact trimer with 11(More)
A high-resolution crystallographic analysis of the nitrogenase MoFe-protein reveals a previously unrecognized ligand coordinated to six iron atoms in the center of the catalytically essential FeMo-cofactor. The electron density for this ligand is masked in structures with resolutions lower than 1.55 angstroms, owing to Fourier series termination ripples(More)
GlnK proteins regulate the active uptake of ammonium by Amt transport proteins by inserting their regulatory T-loops into the transport channels of the Amt trimer and physically blocking substrate passage. They sense the cellular nitrogen status through 2-oxoglutarate, and the energy level of the cell by binding both ATP and ADP with different affinities.(More)
The formate transporter FocA was described to switch its mode of operation from a passive export channel at high external pH to a secondary active formate/H(+) importer at low pH. The crystal structure of Salmonella typhimurium FocA at pH 4.0 shows that this switch involves a major rearrangement of the amino termini of individual protomers in the pentameric(More)
The Amt/Mep/Rh family of integral membrane proteins comprises ammonium transporters of bacteria, archaea and eukarya, as well as the Rhesus proteins found in animals. They play a central role in the uptake of reduced nitrogen for biosynthetic purposes, in energy metabolism, or in renal excretion. Recent structural information on two prokaryotic Amt proteins(More)
Nitrite (NO(2)(-)) is a central intermediate in the nitrogen metabolism of microorganisms and plants, and is used as a cytotoxin by macrophages as part of the innate immune response. The bacterial membrane protein NirC acts as a specific channel to facilitate the transport of nitrite anions across lipid bilayers for cytoplasmic detoxification. Despite(More)
P(II)-like proteins, such as GlnK, found in a wide variety of organisms from prokaryotes to plants constitute a family of cytoplasmic signaling proteins that play a central regulatory role in the assimilation of nitrogen for biosyntheses. They specifically bind and are modulated by effector molecules such as adenosine triphosphate, adenosine diphosphate and(More)
Formate is a major metabolite in the anaerobic fermentation of glucose by many enterobacteria. It is translocated across cellular membranes by the pentameric ion channel/transporter FocA that, together with the nitrite channel NirC, forms the formate/nitrite transporter (FNT) family of membrane transport proteins. Here we have carried out an(More)
The formate/nitrite transporter (FNT) family of integral membrane proteins comprises pentameric channels for monovalent anions that exhibit a broad specificity for small anions such as chloride, the physiological cargo molecules formate, nitrite, and hydrosulfide, and also larger organic acids. Three-dimensional structures are available for the three known(More)
The flavoprotein WrbA, originally described as a tryptophan (W) repressor-binding protein in Escherichia coli, has recently been shown to exhibit the enzymatic activity of a NADH:quinone oxidoreductase. This finding points toward a possible role in stress response and in the maintenance of a supply of reduced quinone. We have determined the(More)