High - level production of MSH2 from Arabidopsis thaliana : a DNA mismatch repair system key subunit . Biochemical and immunological information concerning DNA mismatch repair proteins from higher plants is currently limited , probably due to their low abundance in vivo . An initial analysis of AtMSH2 gene expression by quantitative real - time RT - PCR indicates that calli and seedlings contain 96.7 and 1.4 cDNA copies per ng RNA , respectively , confirming that this gene is predominantly expressed in rapidly dividing tissues . In order to obtain large quantities of AtMSH2 , the protein was efficiently expressed in an Escherichia coli system . The expressed gene product has an in - frame N - terminal Trx - His ( 6 ) -S - tag . The fusion protein represents about 11% of the soluble protein from IPTG - induced E.coli cells . After a two - step purification procedure the final yield accounts for 0.7 mg / g cells. Digestion of this electrophoretically homogeneous recombinant protein with enterokinase results in an intact protein with only one extra amino acid introduced at the N - terminal end . Purified intact protein was used to induce polyclonal antibodies in rabbits . These antibodies cross - react with a 110 - kDa protein from cauliflower inflorescences . Together , our data describe the transcript level , cloning , expression , purification , and polyclonal antibody preparation of AtMSH2 . This work will surely be useful for carrying out plant mismatch repair assays in vitro and analyzing protein expression after the exposure of plants to various stresses .