his tagged protein - (Jan/03/2012 )

Hi everybody,
I have a question for you..
I have to purchase HIV-1 aspartic proteinase to perform an inhibition assay and Sigma aldrich has only the his-tagged version. Can I buy it?Is it suitable for my test?His-tag are used in the purification process or in affinity test, is it right?Can the presence of it influence my inhibition assay?

Thank you

i guess u need an active proteinase
and usually his tag does not interfere with activity, also, u can check product activity on their website, if its active then u dont need to worry i guess