Figure 5.

Methylation-sensitive restriction analysis of plasmids isolated from bacteria transformed with 4aHhaI or 6aHhaI expression vectors and target vector [Ta2(HhaI)]. Experimental details are essentially as in Figure 4B. (A) Restriction analysis of 4aQ²³⁷HhaI mutant or null vectors and 4aHhaI-specific target vector isolated from co-transformed bacteria. The 940 bp band denoting targeted methylation for 4aQG is shown using an arrow. Evidence of non-specific methylation by the 4QV mutant is shown using asterisks. (B) Left-hand panel shows the results of the bacterial assay described above, for the 6aQG protein. The band denoting targeted methylation is indicated (white arrow). The non-specific band is shown using an asterisk. The right-hand panel shows the effects of a transient increase in 6aQG expression vector copy number on the intensity of the 940 bp band and the appearance of higher molecular weight, targeted methylation related bands that disappear upon EcoRV cleavage (small arrows). Low molecular weight non-specific bands are shown using bracket. H, HhaI; V, HhaI + EcoRV restriction, throughout this figure. M is marker mix, Kb is 1 kb ladder (NEB).