Immunological screening of standard cDNA libraries in pBR322 vectors: detection of human fibrinogen and prothrombin cDNA clones

Plaque-lift testing of expression vector lambda gt11 with gold-labeled immunoglobulins

Colloidal gold particles were coated with affinity-purified antibodies against the human plasma protein, C1 inhibitor, and used to probe for fusion proteins of C1 inhibitor with beta-galactosidase encoded by recombinant bacteriophage lambda gt11 DNA. Plaque-lift tests were done with recombinant proteins immobilized on nitrocellulose applying anti-C1 inhibitor gold particles followed by the silver enhancement treatment. This procedure resulted in a sensitive and specific staining of the recombinant proteins and allowed the selective detection of relevant clones in a complex cDNA expression library. Under optimized conditions, plaque-lift testing was completed within 2.5 h after removal of nitrocellulose filters from the plate. Hence, the immunogold detection method provides an alternative to conventional enzyme- or radionuclide-based screening procedures for cDNA expression libraries.

Immunological detection of cDNA clones encoding the uncoupling protein of brown adipose tissue: evidence for an antigenic determinant within the C-terminal eleven amino acids

Poly(A)+RNA was isolated from brown adipose tissue of cold acclimated rats and a fraction enriched for uncoupling protein mRNA was used to generate a cDNA library in pBR 322. Immunological screening of 1,500 colonies with an affinity-purified antiserum against the uncoupling protein yielded five positive clones, pUCPrat1-5. Clone pUCPrat2 encoded the C-terminal 54 amino acids of rat uncoupling protein and exhibited 90% amino acid homology with the hamster protein. Clones pUCPrat3-5 encoded only the C-terminal 11 amino acids suggesting that an antigenic determinant lies within this sequence.