No abstract

A monoclonal antibody of class IgG (subclass IgG1) has been prepared to rabbit brain GABA transaminase (GABA-T). This antibody reveals a single band of molecular weight 52,000 on a nitrocellulose filter blotted with purified GABA-T. On a filter blotted with unfractionated rabbit brain supernatant a major band of molecular weight 58,000 is revealed. An immunoaffinity column was prepared by coupling proteins from ascites fluid containing anti-rabbit GABA-T antibody to Bio-Rad Affi-Gel 15. This column bound purified GABA-T and extracted from unfractionated rabbit brain supernatant a protein of molecular weight 58,000, which was almost homogeneous and which had GABA-T enzyme activity. Using immunoaffinity chromatography, therefore, a high degree of purification of GABA-T may be achieved in a single step. Further, this technique may preserve an authentic form of the enzyme that is lost during the conventional purification procedure. The antibody inhibits GABA-T enzyme activity, up to a maximum of 35%.

Branch Migration ComplexUniversity of East Anglia, Norwich, U.K.Colicins are protein toxins secreted by bacteria during times of nutrient or environmental stress as a means of reducing competition from other microbial populations. These mulitdomain toxins parasitize existing nutrient import pathways, such as those responsible for iron and vitamin uptake, analogous to bacteriophage infection. Through these routes they are able to deliver cytotoxic domains such as ionophores into the periplasmic space. Our work has focused on endonuclease colicins which have to traverse both membranes of an E.coZi cell in order to deliver a 15 kDa, non-specific DNase domain to the cytoplasm. DNase colicin-producing bacteria avoid suicide by co-expressing a small acidic immunity protein which binds to the DNase and neuhalizes its activity. The presentation will focus on the mode of action of the immunity protein Im9. lm9 folds into its distorted antiparallel 4-helix bundlestructure in