RESUMEN
A 10-month-old male chow chow mixed breed dog was presented for anuria secondary to inadvertent prostatectomy performed during unilateral cryptorchidectomy. Surgical repair was successfully performed; however, this resulted in suture-associated urolith formation 3 months later, requiring a second surgical intervention and urethrostomy.
Asunto(s)
Criptorquidismo/veterinaria , Prostatectomía/veterinaria , Suturas/veterinaria , Urolitiasis/veterinaria , Animales , Criptorquidismo/complicaciones , Criptorquidismo/cirugía , Perros , Masculino , Complicaciones Posoperatorias/veterinaria , Prostatectomía/efectos adversos , Suturas/efectos adversos , Urolitiasis/etiología , Urolitiasis/cirugíaRESUMEN
Histidine phosphorylation is important in prokaryotes and occurs to the extent of 6% of total phosphorylation in eukaryotes. Nevertheless phosphohistidine residues are not normally observed in proteins due to rapid hydrolysis of the phosphoryl group under acidic conditions. Many rapid processes employ phosphohistidines, including the bacterial phosphoenolpyruvate:sugar phosphotransferase system (PTS), the bacterial two-component systems and reactions catalyzed by enzymes such as nucleoside diphosphate kinase and succinyl-CoA synthetase. In the PTS, the NMR structure of the phosphohistidine moiety of the phosphohistidine-containing protein was determined but no X-ray structures of phosphohistidine forms of PTS proteins have been elucidated. There have been crystal structures of a few phosphohistidine-containing proteins determined: nucleoside diphosphate kinase, succinyl-CoA synthetase, a cofactor-dependent phosphoglycerate mutase and the protein PAE2307 from the hyperthermophilic archaeon Pyrobaculum aerophilum. A common theme for these stable phosphohistidines is the occurrence of ion-pair hydrogen bonds (salt bridges) involving the non-phosphorylated nitrogen atom of the histidine imidazole ring with an acidic amino acid side chain.
Asunto(s)
Histidina/análogos & derivados , Histidina/metabolismo , Cristalografía por Rayos X , Histidina/química , Enlace de Hidrógeno , Nucleósido-Difosfato Quinasa/química , Sistema de Fosfotransferasa de Azúcar del Fosfoenolpiruvato/química , Sistema de Fosfotransferasa de Azúcar del Fosfoenolpiruvato/metabolismo , Fosfoglicerato Mutasa/química , Fosforilación , Succinato-CoA Ligasas/química , Succinato-CoA Ligasas/metabolismoRESUMEN
Phosphoenolpyruvate carboxykinase (PCK) reversibly catalyzes the carboxylation of phosphoenolpyruvate to oxaloacetate. Carbon dioxide, and not bicarbonate ion, is the substrate utilized. Assays of the carboxylation reaction show that initial velocities are 7.6-fold higher when CO(2) is used instead of HCO(3)(-). Two Escherichia coli PCK-CO(2) crystal structures are presented here. The location of CO(2) is the same for both structures; however the orientation of CO(2) is significantly different, likely from the presence of a manganese ion in one of the structures. PCK and the other three known protein-CO(2) crystal structure complexes have been compared; all have CO(2) hydrogen bonding with a basic amino acid side chain (Arg65 or Lys213 in PCK), likely to polarize CO(2) to make the central carbon atom more electrophilic and thus more reactive. Kinetic studies found that the PCK mutant Arg65Gln increased the K(M) for substrates PEP and oxaloacetate but not for CO(2). The unchanged K(M) for CO(2) can be explained since the Arg65Gln mutant likely maintains a hydrogen bond to one of the oxygen atoms of carbon dioxide.
Asunto(s)
Dióxido de Carbono/metabolismo , Fosfoenolpiruvato Carboxiquinasa (ATP)/metabolismo , Sitios de Unión , Dióxido de Carbono/química , Catálisis , Cinética , Modelos Moleculares , Mutagénesis Sitio-Dirigida , Oxaloacetatos/metabolismo , Fosfoenolpiruvato/metabolismo , Fosfoenolpiruvato Carboxiquinasa (ATP)/química , Fosfoenolpiruvato Carboxiquinasa (ATP)/genética , Unión Proteica , Relación Estructura-Actividad , Difracción de Rayos XRESUMEN
Diffraction data have been collected from a crystal of Thermotoga maritima mannitol dehydrogenase at the Canadian Light Source. The crystal diffracted to 3.3 A resolution and belongs to space group P2(1)2(1)2(1), with unit-cell parameters a = 83.43, b = 120.61, c = 145.76 A. The structure is likely to be solved by molecular replacement.
Asunto(s)
Manitol Deshidrogenasas/química , Thermotoga maritima/enzimología , Cristalización , Cristalografía por Rayos X , Conformación ProteicaRESUMEN
The structure of MosA, a dihydrodipicolinate synthase and reported methyltransferase from Sinorhizobium meliloti, has been solved using molecular replacement with Escherichia coli dihydrodipicolinate synthase as the model. A crystal grown in the presence of pyruvate diffracted X-rays to 2.3 A resolution using synchrotron radiation and belonged to the orthorhombic space group C222(1), with unit-cell parameters a = 69.14, b = 138.87, c = 124.13 A.