polyprotein processing

[JEAN at BIO.TAMU.EDU]

I am analyzing polyprotein processing by in vitro translation of large 
transcripts encoding polypeptides in excess of 200-kDa.  Presently I am 
capable of translating peptides of a maximal size of 120 k-Da in a wheat 
germ or rabbit reticulocyte lysate.  Does anyone have infomation or tips 
that would help me to translate viral polypeptides of 200-400-kDa in either 
of these extracts.