Metylation-free strain ?

Rafael Maldonado rafael at
Thu May 18 16:43:50 EST 1995

On 18 May 1995, Stefan Baeckstroem wrote:

> How do I know if a strain metylates my plasmid or not ?
> I'm using JM109 and DH5alpha.  
> --
> 		Stefan Backstrom
> 		seab at

What kind of methylation? In coli threre are three methylases:

dam: methylation of adenines in the sequence GATC
dcm: methylation of cytosines in CCWGG
EcoK: methylation of adenine in AAC(N6)GTGC and GCAC(N6)GTT
(the last system is very bad known)

You need mutations in those genes. Your strains are both dam+ dcm+. 
JM110 is dam- dcm-. You can get it from the E. coli genetic stock center, 
I guess.


Rafael Maldonado                             |  "y es que...	  
room 6160 Eccles Institute of Human Genetics |   habemos gente pa to'"
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