title: In situ distribution of EcoRI methylase and restriction endonuclease in cells of Escherichia coli Bs 5.
abstract: Specific IgG antibodies were raised in rabbits against purified EcoRI methylase and restriction endonuclease. Post embedding labeling experiments, using the protein A-gold technique, were made with paraformaldehyde-glutaraldehyde fixed cells, embedded in Lowicryl K4M resin at low temperatures. Labeling with methylase-specific antibodies showed 60-70% of gold particles in the cytoplasm and 30-40% at the cell envelope, whereas the use of restriction enzyme-specific antibodies led to a distribution of 10-30% in the cytoplasm and 70-90% in the cell envelope. The results coincide with the proposed function of the enzymes: in the cytoplasm methylase protects the cells' own DNA from self-destruction, and the restriction endonuclease cuts foreign DNA when entering the cell.
mesh_terms: D002451:Cell Compartmentation; D004262:DNA Restriction Enzymes / Q000378:metabolism*; D015246:Deoxyribonuclease EcoRI; D004926:Escherichia coli / Q000201:enzymology* / Q000648:ultrastructure; D006046:Gold; D007158:Immunologic Techniques; D008780:Methyltransferases / Q000378:metabolism*; D008854:Microscopy, Electron; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific)
chemical_list: D006046:Gold; C020098:DNA modification methylase EcoRI; D008780:Methyltransferases; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); D004262:DNA Restriction Enzymes; D015246:Deoxyribonuclease EcoRI