problems with protein expression

[Qingwu Shen]

Hi everybody,

I'm trying to expression some rabbit skeletal TnI using E.coli. The plasmid I'm 
using came from some other lab and has been stored in freezer for many years. I'm 
using Rossetta (DE3) PlysS to express protein and the yield is very low. Even 
worse after I changed two Cys to Ser in the protein using PCR mutagenesis, I got 
no protein (mutant TnI) expression although there was a induction band on SDS -
PAGE gel when compared the induced sample to non-induced control. Could anybody 
help me to figure out this problems? I just started to express protein using 
E.coli. Any help is highly appreciated.

Shen