Heavy
Chains
In
IgG
each
heavy
chain
(H)
consists
of
about
450
amino
acid
residues,
of
which
about
the
first
121
make
up
the
variable
region
(VH)
and
the
remainder
the
constant
region
(CH).
The
constant
region
is
thus
about
three
times
the
length
of
the
variable
region.
In
the
CH
region
much
of
the
sequence
is
repeated
after
about
every
110
residues.
This
results
in
three
domains
(CH1,
CH2
and
CH3),
which
are
about
equal
in
length
and
have
similar
sequences.
