[UV- and CD-spectra of restriction endonuclease EcoRII and DNA-methylase EcoRII]

UV- and CD-spectra of homogeneous enzymes have been measured. Extinction coefficients estimated from the UV-spectra are 0.97 for restriction endonuclease EcoRII at 279.5 nm and 1.17 for DNA-methylase EcoRII at 279 nm. As it follows from the CD spectra, both enzymes have a well developed tertiary structure and a highly ordered secondary structure, which consists of 22% alpha-helices, 64% beta-structure and 9% bends for REcoRII and of 44% alpha-helices, 48% beta-structure and 4% bends for MEcoRII. Restriction endonuclease denatures at 50 degrees C, while DNA-methylase denatures at 45 degrees C, with partial reversibility upon cooling.