Length of spacer in His-tag fusion vector

[Namjin Chung]

Dear Netters,

I would like to thank you who have responded to my question about mammalian expression 
vectors with C-terminal His-tag.  In addition to Invitrogen vectors which with N-terminal 
His-tag, most of responses referred Qiagen and Novagen for C-terminal His-tag fusion 
protein vectors.  They do have C-terminal vectors, but not for mammalian expression.

I wonder I should construct C-terminal His-tag vectors by myself.  At this moment, I would 
ask you all again about proper length of amino acid spacer between C-terminus of my 
protein and hexahistidine residues.  Someone told me that 5-10 aa would be good for 
N-terminal fusion, but I really don't know if this is also good for C-terminal fusion.  Thank 
you for suggestions in advance.

Namjin Chung 
Duke University Medical Center