pGEX-4T Expression Vector Problems

Mark Jason Logan mjlogan at
Thu Mar 17 12:16:01 EST 1994

What does the cDNA encode for?  Have you tried seqencing your clones to
see if there are any deletions, rearrangements etc?  Many times when you
see poor transformation efficiencies it is due to the production of a toxic
gene product.  In fact if you get transformation efficiencies less then
50% relative to a control then I would almost bet that you have a toxic
protein.  I am not familiar with the expression system you are using but
even in T7 promoter systems basal expression occurs and may cause you to
have poor transformation due to a toxic gene product.  I really can say
much more until I can look and see what type of vector you are using.  If
this doesn't help you can e-mail me at mjlogan at

Good luck


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