Alda Navaza

Redox signalling in the chloroplast: structure of oxidized pea fructose‐1,6‐bisphosphate phosphatase

Sunlight provides the energy source for the assimilation of carbon dioxide by photosynthesis, but it also provides regulatory signals that switch on specific sets of enzymes involved in the alternation of light and dark metabolisms in chloroplasts. Capture of photons by chlorophyll pigments triggers redox cascades that ultimately activate target enzymes via the reduction of regulatory disulfide bridges by thioredoxins. Here we report the structure of the oxidized, low‐activity form of chloroplastic fructose‐1,6‐bisphosphate phosphatase (FBPase), one of the four enzymes of the Calvin cycle whose activity is redox‐regulated by light. The regulation is of allosteric nature, with a disulfide bridge promoting the disruption of the catalytic site across a distance of 20 Å. Unexpectedly, regulation of plant FBPases by thiol–disulfide interchange differs in every respect from the regulation of mammalian gluconeogenic FBPases by AMP. We also report a second crystal form of oxidized FBPase whose tetrameric structure departs markedly from D2 symmetry, a rare event in oligomeric structures, and the structure of a constitutively active mutant that is unable to form the regulatory disulfide bridge. Altogether, these structures provide a structural basis for redox regulation in the chloroplast.

Structure–function analysis of the antiangiogenic ATWLPPR peptide inhibiting VEGF165 binding to neuropilin-1 and molecular dynamics simulations of the ATWLPPR/neuropilin-1 complex

Heptapeptide ATWLPPR (A7R), identified in our laboratory by screening a mutated phage library, was shown to bind specifically to neuropilin-1 (NRP-1) and then to selectively inhibit VEGF(165) binding to this receptor. In vivo, treatment with A7R resulted in decreasing breast cancer angiogenesis and growth. The present work is focused on structural characterization of A7R. Analogs of the peptide, obtained by substitution of each amino acid with alanine (alanine-scanning) or by amino acid deletion, have been systematically assayed to determine the relative importance of the side chains of each residue with respect to the inhibitory effect of A7R on VEGF(165) binding to NRP-1. We show here the importance of the C-terminal sequence LPPR and particularly the key role of C-terminal arginine. In solution, A7R displays significant secondary structure of the backbone adopting an extended conformation. However, the functional groups of arginine are very flexible in the absence of NRP-1 pointing to an induced fit upon binding to the receptor. A MD trajectory of the A7R/NRP-1 complex in explicit water, based on the recent tuftsin/NRP-1 crystal structure, has revealed the hydrogen-bonding network that contributes to A7Rs binding activity.

Recombinant plant gamma carbonic anhydrase homotrimers bind inorganic carbon

MINT‐7266036: gamma CA2 (uniprotkb:Q9C6B3) and gamma CA2 (uniprotkb:Q9C6B3) physically interact (MI:0914) by molecular sieving (MI:0071)

Geometrical and inclusion considerations in the formation of hexagonal nanotubes of calix[4]arene di-methoxycarbonyl methyl ester and acid

The crystal structures of calix[4]arene di-methoxycarbonyl-methyl ester and carboxylic acid have been resolved. Interestingly, the packing for both molecules is in the form of crystal symmetry defined hexagonal helical nanotube architecture, but with the methyl ester derivative showing an extended form of the helix with regard to that formed by the carboxylic acid derivative. The addition of one carbon in the ester group leads to inclusion of the ethyl ester within a neighbouring calixarene cavity, and in consequence the packing becomes radically different.

Solid-state caging of 1,10-phenanthroline π–π stacked dimers by calix[4]arene dihydroxyphosphonic acid

The calix[4]arene dihydroxyphosphonic acid-1,10-phenanthroline complex shows caging of the guest molecules as a pi-pi stacked dimer in a cavity formed by intermolecular hydrogen bonds and aromatic walls formed by the calixarene.

Solid state structures of the complexes between the antiseptic chlorhexidine and three anionic derivatives of calix[4]arene

The solid state structures of the complexes between antiseptic chlorhexidine and three anionic calix[4]arene derivatives are described. Each of the three calixarenes shows typical self-organisation in the solid-state that will further impose a specific complexation of the active molecule in the co-crystal.

A new packing motif for para-sulfonatocalix[4]arene: the solid state structure of the para-sulfonatocalix[4]arene D-arginine complex

The solid-state structure of the complex of para-sulfonatocalix[4]arene with d-arginine, contains a water channel diagonal to a zigzag bilayer of the host, within the bilayer six crystallographically independent molecules of arginine are present, four being included in the calix cavities.

The crystal and molecular structure of sodium hexacyanoosmate(II) decahydrate and related hexacyanometalate complexes

The crystal structures of sodium hexacyanoosmate, ruthenate and ferrate decahydrates, Na4M(CN)6·10H2O(M=Os, Ru, Fe), have been determined from X-ray diffraction data and refined by full matrix least-squares to final agreement values: R = 0.038, Rw = 0.039; R = 0.026, Rw = 0.041; R = 0.060, Rw = 0.043 for Os, Ru and Fe compounds, respectively. The compounds are isostructural and crystallize in the monoclinic space group P21/n, Z = 2, with a = 9.154, b = 11.506, c = 9.876 A, β = 97.95°; a = 9.146, b = 11.486, c = 9.867 A, β = 98.00°; a = 9.038, b = 11.450, c = 9.782 A, β = 97.57°, for Os, Ru and Fe compounds, respectively. The structure can be described as layers of hexacyanometallate anions, intercalated with layers of sodium polyhedra containing hydration water molecules and N atoms, perpendicular to the crystallographic ac plane. MetalC and CN distances for the hexacyanide anions are correlated with those from other structurally related moieties. The infrared spectra of the compounds are complementary with previous results for potassium salts.

Helical aquatubes of calix[4]arene di-methoxycarboxylic acid

Two trimeric units of calix[4]arene di-methoxycarboxylic acid form a six-pointed star architecture that, in turn, generates triple helical aquatubes which intermesh between themselves by aromatic-aromatic interdigitation of the macrocycle.

The structure of a self-assembled calixarene aqua-channel system

The crystal structure of the complex 12.calix-[4]-arene dihydroxyphosphonic acid, 12.propane diammonium, 12.ethanol and 40.water molecules is based on dimeric units of the calix, assembled via trigonal units into a hexameric tube of 15 A radius and 16 A depth, further assemby via spanning propane diammonium cations and ethanol molecules forms a channel (40 A), selectively containing all the water molecules.