Helper Phage missing gIII ??

Chris Noren noren at
Thu Jun 9 12:53:44 EST 1994

In article <Cr4G8v.M0z at>, ptk at (Peter
Kristensen) wrote:

> Could anyone help me with information on a helper phage missing gIII.
> I would like to get full representation of fusion protein on protein III
> of the filamenteus phage of the M-13 type.
> thanks in advance

The gene III protein is necessary for phage infectivity (binds to F-pilus
on cell in initial infection event), so deletion of gIII would result in a
helper phage that won't superinfect!! If you want full representation of
fusion on phage, you should either use a phage vector (only good for small
proteins and peptides) or a phagemid where the fusion is under control of a
very strong (but regulatable!!) promoter. You can also try a gVIII fusion,
where 10% fusion representation would still be 270 copies/phage (as opposed
to 5 copies for gIII wth full representation).

Christopher Noren
New England Biolabs
(800)632-5227 ext 261
noren at

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