IUBio

What is the prime (') in F(ab)'2

Ken Frauwirth BioKen frauwirt at notmendel.Berkeley.EDU
Thu Sep 21 04:27:25 EST 1995


In article <43pqcu$gfk at netnews.upenn.edu>,
David Peritt  <Peritt_d at a1.mscf.upenn.edu> wrote:

                    [snip]

>
>I find your description of Fab generation fascinating and your details
>impecable BUT...
>What is the (') that you put after Fab' or F(ab)'2.  The little mark that
>sits above the letter b is called prime.  Why is it there.  I am
>begginning to think it is a vestibular mark like the appendix but the
>history of this mark is what I seek....

The "prime" is simply to indicate that the fragments are not *quite* the same
as Fab (as already mentioned, the Fab' is slightly larger and contains a
cysteine that can take part in an interchain disulfide).  The "prime" is used 
rather extensively in biology and chemistry nomenclature.  For example, the 
atoms in ATP are numbered such that the adenine atoms are 1, 2, 3,... 
while the ribose atoms are 1', 2', 3' ...  I'm sure you are familiar with the 
3'/5' nomenclature of nucleic acids - it is just to distinguish between the 
two ring systems in the nucleotides.  If memory serves, RNA polymerase is 
another example.  It is composed of several subunits, including 2 alphas, a 
beta, and a beta prime.  Beta and beta prime are very similar, but are not 
identical, so the prime is used to distinguish them.

While there may be another, more interesting origin for the "prime", I suspect
that it is this rather mundane one that is correct.

Hope that helps,

BioKen
-- 
Ken Frauwirth (MiSTie #33025)                         _           _
frauwirt at mendel.berkeley.edu                         |_) *    |/ (_ |\ |
http://mendel.berkeley.edu/~frauwirt/HomePage/       |_) | () |\ (_ | \|  
DNRC Title: Chairman of Joint Commission on In-duh-vidual Affairs



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