RESUMEN
The complex of concanavalin A with methyl alpha-D-glucopyranoside crystallizes as regular rhombic dodecahedra containing 35% protein by weight. The crystal is of space group I23 with a = 167.8 A (1 A = 0.1 nm) and contains one concanavalin A dimer per asymmetric unit. It diffracts to a resolution of 1.9 A and is suitable for crystallographic investigation of the structure of the saccharide-binding site.
Asunto(s)
Concanavalina A/metabolismo , Metilglucósidos/metabolismo , Metilglicósidos/metabolismo , Sitios de Unión , Cristalización , Cristalografía , Sustancias Macromoleculares , Difracción de Rayos XRESUMEN
X-ray crystallographic data from four crystal forms of Escherichia coli bacterioferritin show that the molecule has a diameter in the range 119 to 128 A. Molecules are composed of 24 subunits arranged in 432 symmetry. In both size and symmetry the molecule resembles ferritin from eukaryotes. The four crystal forms are monoclinic, space group P2(1) with unit cell dimensions a = 118.7 A, b = 211.6 A, c = 123.3 A and beta = 119.1 degrees; orthorhombic, C222(1), a = 128.7 A, b = 197.1 A, c = 202.8 A; tetragonal, P4(2)2(1)2, a = b = 210.6 A, c = 145.0 A and cubic, I432, a = 146.9 A.
Asunto(s)
Proteínas Bacterianas , Grupo Citocromo b , Ferritinas , Escherichia coli , Difracción de Rayos XRESUMEN
The 13C epsilon NMR signal of methionine sulfoxide is 22.6 ppm downfield from that of methionine. This affords a method by which the extent of methionine oxidation can be determined in intact protein. We demonstrate the utility of this approach with beta-galactosidase enriched with 13C in its methionine methyls.
Asunto(s)
Metionina/análogos & derivados , Proteínas , Compuestos de Tosilo , Cloraminas , Escherichia coli/enzimología , Espectroscopía de Resonancia Magnética , Metionina/análisis , Oxidación-Reducción , Sulfóxidos/análisis , beta-GalactosidasaAsunto(s)
Hidrógeno , Lectinas , Oxígeno , Sitios de Unión , Calcio , Cromatografía por Intercambio Iónico , Concanavalina A , Glicósidos , Concentración de Iones de Hidrógeno , Espectroscopía de Resonancia Magnética , Manganeso , Matemática , Isótopos de Oxígeno , Unión Proteica , Espectrofotometría UltravioletaAsunto(s)
Proteínas de Plantas , Piranos , Calcio , Isótopos de Carbono , Fenómenos Químicos , Química , Cinética , Magnesio , Manganeso , Unión ProteicaAsunto(s)
Concanavalina A , Zinc , Sitios de Unión , Calcio , Ligandos , Análisis Espectral , Rayos XAsunto(s)
Concanavalina A/metabolismo , Metilglicósidos/metabolismo , Células Fotorreceptoras/metabolismo , Animales , Sitios de Unión , Radioisótopos de Cobalto , Técnicas In Vitro , Ligandos , Membranas/análisis , Membranas/metabolismo , Metilglicósidos/análisis , Peso Molecular , Células Fotorreceptoras/análisis , Unión ProteicaAsunto(s)
Proteínas de Plantas , Difracción de Rayos X , Calcio , Cristalización , Manganeso , MetalesAsunto(s)
Concanavalina A , Sitios de Unión , Calcio , Manganeso , Modelos Moleculares , Conformación Proteica , Difracción de Rayos XAsunto(s)
Concanavalina A/química , Lectinas/química , Manganeso/química , Sitios de Unión , Metabolismo de los Hidratos de Carbono , Carbohidratos/química , Concanavalina A/metabolismo , Cristalografía por Rayos X , Lectinas/metabolismo , Manganeso/metabolismo , Modelos Moleculares , Conformación Proteica , Análisis Espectral , TermodinámicaRESUMEN
Binding of a transition metal ion to specific sites in concanavalin A induces the formation of specific Ca(2+) ion-binding sites. Sites for binding alpha-methyl d-glucopyranoside exist only when a transition metal ion and Ca(2+) ion are bound.
Asunto(s)
Sitios de Unión , Metales , Proteínas de Plantas , Calcio , Fenómenos Químicos , Química , Cobre , Glucógeno , NíquelRESUMEN
The complex of methyl alpha-D-arabinofuranoside with concanavalin A crystallizes in the orthorhombic space group P2(1)22(1) with cell dimensions a = 97.5, b = 87.0 and c = 61.5 A. The asymmetric unit contains one dimer and the unit cell consists of two tetrahedral clusters of point-group symmetry 222. The crystals diffract to 2.0 A resolution.
RESUMEN
. A low-resolution partial structure of bacterioferritin was solved using a combination of molecular replacement and rigid-body refinement methods. Modification of bacterioferritin crystals by soaking in tetrachloroplatinate results in a phase transition from tetragonal symmetry (space group P4(2)2(1)2) to a pseudo-cubic one (approximate space group I432). Helical parts of human H ferritin structure stripped of side chains beyond the C(beta) atoms were used as the model. An electron-density map of the refined model revealed a region of extended density which by its shape and position in a pocket between helices was identified as haem. Inclusion of haem in the refinement showed that it can occupy only one of two symmetry-related sites near a twofold axis of the molecule.
RESUMEN
Bacterioferritin of Escherichia coli, also known as cytochrome b1, is a hollow, nearly spherical shell made up of 24 identical protein subunits and 12 haems. We have solved this structure in a tetragonal crystal form at 2.9 A resolution. We find that each haem is bound in a pocket formed by the interface between a pair of symmetry-related subunits. The quasi-twofold axis of the haem is closely aligned with the local twofold axis relating these subunits. The axial ligands of the haem are sulphurs of two equivalent methionyl residues (Met 52) from the symmetry-related subunits. A cluster of four water molecules is trapped in the gap between the upper edge of the haem and two extended protein loops which close off the haem from the outer aqueous environment. This is the first structure of a bis-methionine ligated haem-binding site and the first case of a twofold symmetric haem-binding site.
Asunto(s)
Proteínas Bacterianas/química , Grupo Citocromo b/química , Ferritinas/química , Hemo/metabolismo , Modelos Moleculares , Conformación Proteica , Proteínas Bacterianas/metabolismo , Sitios de Unión , Cristalografía por Rayos X , Grupo Citocromo b/metabolismo , Escherichia coli/química , Ferritinas/metabolismo , Enlace de Hidrógeno , Datos de Secuencia MolecularRESUMEN
The Zn site in concanavalin A solution was studied by X-ray absorption fine structure spectroscopy (XAFS) with and without the saccharide methyl alpha-D-glucoside (aMG) bound to the protein. No structural change occurs in the metal-binding site when the saccharide is bound to the protein. There is, however, evidence for structural change remote from the metal site. This is in contrast to the significant changes that we have previously found to occur in the near neighborhood of the Zn atom when an aqueous solution of Zn concanavalin A crystallizes. We propose a structural explanation of these facts based on the known crystal structure of concanavalin A.