RESUMEN
The ubiquitin fold is a versatile and widely used targeting signal that is added post-translationally to a variety of proteins. Covalent attachment of one or more ubiquitin domains results in localization of the target protein to the proteasome, the nucleus, the cytoskeleton or the endocytotic machinery. Recognition of the ubiquitin domain by a variety of enzymes and receptors is vital to the targeting function of ubiquitin. Several parallel pathways exist and these must be able to distinguish among ubiquitin, several different types of polymeric ubiquitin, and the various ubiquitin-like domains. Here we report the first molecular description of the binding site on ubiquitin for ubiquitin C-terminal hydrolase L3 (UCH-L3). The site on ubiquitin was experimentally determined using solution NMR, and site-directed mutagenesis. The site on UCH-L3 was modeled based on X-ray crystallography, multiple sequence alignments, and computer-aided docking. Basic residues located on ubiquitin (K6, K11, R72, and R74) are postulated to contact acidic residues on UCH-L3 (E10, E14, D33, E219). These putative interactions are testable and fully explain the selectivity of ubiquitin domain binding to this enzyme.
Asunto(s)
Mutagénesis Sitio-Dirigida , Resonancia Magnética Nuclear Biomolecular , Tioléster Hidrolasas/química , Tioléster Hidrolasas/metabolismo , Ubiquitinas/química , Ubiquitinas/metabolismo , Sitio Alostérico , Secuencia de Aminoácidos , Simulación por Computador , Secuencia Conservada/genética , Cristalografía por Rayos X , Humanos , Modelos Moleculares , Datos de Secuencia Molecular , Mutación , Papaína/química , Papaína/metabolismo , Conformación Proteica , Alineación de Secuencia , Electricidad Estática , Especificidad por Sustrato , Ubiquitina Tiolesterasa , Ubiquitinas/genéticaAsunto(s)
Cesárea , Enfermedades Fetales/fisiopatología , Neoplasias de Cabeza y Cuello/fisiopatología , Circulación Placentaria , Teratoma/fisiopatología , Adulto , Obstrucción de las Vías Aéreas/prevención & control , Anestesia General , Femenino , Enfermedades Fetales/diagnóstico por imagen , Neoplasias de Cabeza y Cuello/congénito , Neoplasias de Cabeza y Cuello/diagnóstico por imagen , Humanos , Recién Nacido , Embarazo , Mecánica Respiratoria/efectos de los fármacos , Teratoma/congénito , Teratoma/diagnóstico por imagen , Resultado del Tratamiento , Ultrasonografía PrenatalRESUMEN
BACKGROUND: Angiotensin II may prove useful in treating regional anesthesia-induced hypotension in obstetric patients, because it causes less uterine vasoconstriction than do other vasoconstrictor drugs (such as phenylephrine). This study compared (1) maternal blood pressure and heart rate and (2) fetal status at delivery in parturients given either prophylactic angiotensin II or ephedrine infusion during spinal anesthesia for elective cesarean delivery. METHODS: Fifty-four women were randomized to receive either angiotensin II or ephedrine infusion intravenously during spinal anesthesia for elective cesarean section delivery. Simultaneous with subarachnoid injection, infusion of angiotensin II (2.5 microg/ml) or ephedrine (5 mg/ml) was initiated at 10 ng x kg(-1) x min(-1) and 50 microg x kg(-1) x min(-1), respectively. The rate of each infusion was adjusted to maintain maternal systolic blood pressure at 90-100% of baseline. RESULTS: Cumulative vasopressor doses (mean+/-SD) through 10, 20, and 30 min were 150+/-100, 310+/-180, and 500+/-320 ng/kg in the angiotensin group and 480+/-210, 660+/-390, and 790+/-640 microg/kg in the ephedrine group. Maternal heart rate was significantly higher (P < 0.001) during vasopressor infusion in the ephedrine group than in the angiotensin group. Umbilical arterial and venous blood pH and base excess were all significantly higher (P < 0.05) in the angiotensin group than in the ephedrine group. CONCLUSIONS: Angiotensin II infusion maintained maternal systolic blood pressure during spinal anesthesia without increasing maternal heart rate or causing fetal acidosis.