size of Ab H chain V region?

George Johnson johnson at
Fri Oct 6 23:23:14 EST 1995

In article <ralph.1163388561D at> ralph at (R M Bernstein) writes:
>In Article <199510061545.IAA18380 at>, dmullins at (David W.
>Mullins) wrote:
>>How long is the V region of an Ab H chain?
>>Some say 113, others 123 amino acid residues?
>>What is the correct (or *most current*) answer?  Please help!
>>Thanks for your assistance,
>especially of igm's , can be huge.  if you go to Dr.TT Wu's homepage, where
>he has all the kabat and wu stuff set up, you can paruse the vhs of any
>creature extant! (and cloned).

The length of the heavy chain variable region varies.  The 113 length you
found is probably due to forcing the sequence to fit the Kabat alignment.
The 123 length is the common length of light chains, using residue 
counting, with Kabat alignment.

As you heard, the length of the 3rd hypervariable region can be very long.
Some unusual antibodies with very long CDR3s are thought to slip into reactive
cavities of antigens.

The usual length, in residues, of a heavy chain is about 133 amino acids, give
or take 10 residues.  Remember this is only the variable region.

If you need exact statistics, let me know.  We can do a quick count of lengths
if this is necessary.

George Johnson
Kabat Database 

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