GST fusion protein cleavage problem

[Miss. L Somerville]

I have a GST-G-CSF fusion protein expressed using the baculovirus
expression system. I have purified it using Pharmacia's glutathione
sepharose 4B purification columns and carried out the cleavage on the
column as well as in free solution.  However I cannot cleave the GST away
from the G-CSF even though I am using x2 the concentration Pharmacia
recommend and for a longer period of time.  Any suggestions would be
greatly apprecaited.  Thanks

Linda Somerville
l.somerville at qub.ac.uk