DOES BCGI, A UNIQUE RESTRICTION-ENDONUCLEASE, REQUIRE 2 RECOGNITION SITES FOR CLEAVAGE

Bcgl is a multi-subunit restriction-modification (R-M) complex. Bcgl p refers pBR322 DNA over pUC19 in a DNA cleavage reaction. Linearized pB R322 contains two Bcgl recognition sites and pUC19 has only one site. To test whether two target sites are required for Bcgl cleavage, one o f the two sites in pBR322 was deleted, and as a result pBR322-1 became a poor substrate for Bcgl. Conversely, adding a Bcgl site to pUC19 ma kes it a much better substrate for Bcgl cleavage. In addition, the Bcg l (R-M) complex forms a heterohexamer in solution that is capable of i nteracting with two recognition sites. Our results suggest that Bcgl r equires two recognition sites for cleavage.