ABSTRACT
The isoelectric focusing of human thyroglobulin has been studied on slab gels. Three bands, focusing between pH 4.4 and 4.7, are observed. Deglycosylation of thyroglobulin does not affect the distribution of focused bands, but increases the pH range of focusing slightly. Native thyroglobulin and its half-sized subunit show the same distribution of isoelectric bands. Refocusing of one band results in the appearance of the three original bands. It appears that soluble complexes of thyroglobulin with ampholyte account for the apparent heterogeneity observed on isoelectric focusing.
Subject(s)
Isoelectric Focusing , Thyroglobulin/isolation & purification , Ampholyte Mixtures , Glycoside Hydrolases , Humans , Hydrogen-Ion Concentration , Protein DenaturationABSTRACT
The carrier-mediated transport of GABA in rat brain synaptosomes was strongly and permanently inhibited byL-2,4-diaminobutyric acid (DAB). In order to discriminate between carrier-mediated and non-carrier-mediated release of [(3)H]GABA, synaptosomes prelabeled with 0.5 µM [(3)H]GABA in the presence of 100 µM DAB, or with 0.2 µM [(3)H]GABA without DAB, were superfused in conditions stimulating the release of [(3)H]GABA. Only the release elicited by unlabeled GABA or DAB (by homo- and heteroexchange, respectively) was strongly inhibited in DAB-pretreated synaptosomes. The spontaneous release and the release induced by 56 mM KCl in the presence of CaCl2, by the ionophore A23187, by ouabain, by lack of K(+), or by purified black widow spider toxin were unaffected or only barely decreased in DAB-treated synaptosomes, and therefore do not seem to be mediated by the DAB-blocked GABA carrier.
