The functional repressor parts of a tetrameric lac repressor-beta-galactosidase chimaera are organized as dimers.
AUTOR(ES)
Kania, J
RESUMO
The chimaeric protein repressor-galactosidase, in which fully active lac repressor is covalently linked to the active enzyme beta-galactosidase, was used as a system for probing the quaternary structure of lac repressor. Electron micrographs revealed repressor-galactosidase to be a tetrameric aggregate. When lac repressor, alone, was crosslinked with dimethyl suberimidate, dimers, trimers, tetramers, and oligomers of the protein subunit were produced, whereas crosslinking of the tetrameric repressor-galactosidase resulted in the production of only dimers of the chimaera. Treatment of lac repressor with iodine resulted in the formation of protein dimers; the same result was obtained with repressor-galactosidase. After limited proteolysis of lac repressor, no crosslinking was obtained after treatment with dimethyl suberimidate, whereas iodine still produced a covalent linkage. These results are interpreted as evidence that the lac repressor parts of the tetrameric repressor-galactosidase-chimaera are organized as dimers on the tetrameric-beta-galactosidase core. Because this chimaera has been previously shown to have normal repressor activity [B. Müller-Hill and J. Kania (1974) Nature, 249,561-563], we conclude that lac repressor still is biologically active as a dimeric aggregate.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=431150Documentos Relacionados
- beta-Galactosidase chimeras: primary structure of a lac repressor-beta-galactosidase protein.
- Assembly of the functional membrane attack complex of human complement: formation of disulfide-linked C9 dimers.
- In vitro synthesis of beta-galactosidase with ilv-lac fusion deoxyribonucleic acid as template.
- The lac operator-repressor system is functional in the mouse
- Taq DNA polymerase blockage at pyrimidine dimers.