Structure of the sodium-dependent phosphate transporter reveals insights into human solute carrier SLC20.

Inorganic phosphate (P) is a fundamental and essential element for nucleotide biosynthesis, energy supply, and cellular signaling in living organisms. Human phosphate transporter (PiT) dysfunction causes numerous diseases, but the molecular mechanism underlying transporters remains elusive. We report the structure of the sodium-dependent phosphate transporter from (PiT) in complex with sodium and phosphate (PiT-Na/Pi) at 2.

Roles of the Hydrophobic Gate and Exit Channel in Vigna radiata Pyrophosphatase Ion Translocation.

Membrane-embedded pyrophosphatase (M-PPase) hydrolyzes pyrophosphate to drive ion (H and/or Na) translocation. We determined crystal structures and functions of Vigna radiata M-PPase (VrH-PPase), the VrH-PPase-2P complex and mutants at hydrophobic gate (residue L555) and exit channel (residues T228 and E225). Ion pore diameters along the translocation pathway of three VrH-PPases complexes (P-, 2P- and imidodiphosphate-bound states) present a unique wave-like profile, with different pore diameters at the hydrophobic gate and exit channel, indicating that the ligands induced pore size alterations.

Membrane pyrophosphatases from Thermotoga maritima and Vigna radiata suggest a conserved coupling mechanism.

Membrane-bound pyrophosphatases (M-PPases), which couple proton/sodium ion transport to pyrophosphate synthesis/hydrolysis, are important in abiotic stress resistance and in the infectivity of protozoan parasites. Here, three M-PPase structures in different catalytic states show that closure of the substrate-binding pocket by helices 5-6 affects helix 13 in the dimer interface and causes helix 12 to move down. This springs a 'molecular mousetrap', repositioning a conserved aspartate and activating the nucleophilic water.

Proton/sodium pumping pyrophosphatases: the last of the primary ion pumps.

Membrane-bound pyrophosphatases (M-PPases) are homodimeric enzymes that couple the generation and utilization of membrane potentials to pyrophosphate (PPi) hydrolysis and synthesis. Since the discovery of the link between PPi use and proton transport in purple, non-sulphur bacteria in the 1960s, M-PPases have been found in all three domains of life and have been shown to have a crucial role in stress tolerance and in plant maturation. The discovery of sodium-pumping and sodium/proton-pumping M-PPases showed that the pumping specificity of these enzymes is not limited to protons, further suggesting that M-PPases are evolutionarily very ancient.

Structural characterizations of the chloroplast translocon protein Tic110.

Tic110 is a major component of the chloroplast protein import translocon. Two functions with mutually exclusive structures have been proposed for Tic110: a protein-conducting channel with six transmembrane domains and a scaffold with two N-terminal transmembrane domains followed by a large soluble domain for binding transit peptides and other stromal translocon components. To investigate the structure of Tic110, Tic110 from Cyanidioschyzon merolae (CmTic110) was characterized.

Crystal structure of the Klebsiella pneumoniae NFeoB/FeoC complex and roles of FeoC in regulation of Fe2+ transport by the bacterial Feo system.

Feo is a transport system commonly used by bacteria to acquire environmental Fe(2+). It consists of three proteins: FeoA, FeoB, and FeoC. FeoB is a large protein with a cytosolic N-terminal domain (NFeoB) that contains a regulatory G protein domain and a helical S domain.

Crystal structure of a membrane-embedded H+-translocating pyrophosphatase.

H(+)-translocating pyrophosphatases (H(+)-PPases) are active proton transporters that establish a proton gradient across the endomembrane by means of pyrophosphate (PP(i)) hydrolysis. H(+)-PPases are found primarily as homodimers in the vacuolar membrane of plants and the plasma membrane of several protozoa and prokaryotes. The three-dimensional structure and detailed mechanisms underlying the enzymatic and proton translocation reactions of H(+)-PPases are unclear.

Structure of the catalytic domain of the Clostridium thermocellum cellulase CelT.

Cellulases hydrolyze cellulose, a major component of plant cell walls, to oligosaccharides and monosaccharides. Several Clostridium species secrete multi-enzyme complexes (cellulosomes) containing cellulases. C.

Structure of the Trichomonas vaginalis Myb3 DNA-binding domain bound to a promoter sequence reveals a unique C-terminal β-hairpin conformation.

Trichomonas vaginalis Myb3 transcription factor (tvMyb3) recognizes the MRE-1 promoter sequence and regulates ap65-1 gene, which encodes a hydrogenosomal malic enzyme that may play a role in the cytoadherence of the parasite. Here, we identified tvMyb3(53-180) as the essential fragment for DNA recognition and report the crystal structure of tvMyb3(53-180) bound to MRE-1 DNA. The N-terminal fragment adopts the classical conformation of an Myb DNA-binding domain, with the third helices of R2 and R3 motifs intercalating in the major groove of DNA.

Crystal structure of Helicobacter pylori spermidine synthase: a Rossmann-like fold with a distinct active site.

Spermidine synthase (putrescine aminopropyltransferase, PAPT) catalyzes the transfer of the aminopropyl group from decarboxylated S-adenosylmethionine to putrescine during spermidine biosynthesis. Helicobacter pylori PAPT (HpPAPT) has a low sequence identity with other PAPTs and lacks the signature sequence found in other PAPTs. The crystal structure of HpPAPT, determined by multiwavelength anomalous dispersion, revealed an N-terminal beta-stranded domain and a C-terminal Rossmann-like domain.

Kinetic and structural properties of inorganic pyrophosphatase from the pathogenic bacterium Helicobacter pylori.

Inorganic pyrophosphatase (PPase) catalyzes the hydrolysis of pyrophosphate (PPi) to orthophosphate (Pi) and controls the level of PPi in cells. PPase plays an essential role in energy conservation and provides the energy for many biosynthetic pathways. The Helicobacter pylori pyrophosphatase (HpPPase) gene was cloned, expressed, purified, and found to have a molecular weight of 20 kDa.