BL21 Codon-plus

Michael L. Sullivan mlsulliv at
Thu Nov 9 09:43:11 EST 2000

I've used the "RIL" cells.  For my protein, there were a lot of rare Arg
codons.  The cells helped a bit, increasing protein expression by about 2
fold (I went from about 1 mg/l to 2 mg/l).  Sorry, not sure about the
answer to your other question.  Perhaps the empirical approach is the best,
i.e. try both types of cells.


>Hi everyone,
>After many efforts, we are not still able to express our recombinant
>human protein in E. coli. so we are thinking to switch to codon-plus
>Someone tried the BL21 codon plus (DE3) strain from Stratagene?

>Another question: there are 2 strains with different tRNAs:
>both have the AGA/AGG tRNA but
>RP posses the CCC tRNA
>RIL posses the AUA and CUA tRNAs
>In my gene I have 6 CCC codons and 4 AUA + 3 CUA codons;
>do you think it's better to overcome the 6CCC problem (RP strain)
>or the 4AUA+3CUA problem?
>In other words are more problematic 6 unusals codons of the
>same type or 7 unusal codons of different types?
>Thank you for your attention.
>Gianluca Molla Ph.D.
>Dept. of Structural and Functional Biology, University of Insubria
>via J.H. Dunant 3, 21100 Varese (ITALY), mail:
>gianluca.molla at
>Tel. ++39-0332-421414 Fax. ++39-0332-421500

Michael L. Sullivan, Ph.D

U.S. Dairy Forage Research Center
1925 Linden Drive West
Madison WI, 53706

(608) 264-5144 Phone
(608) 264-5147 Fax


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