Biology Reference
In-Depth Information
11
Immunologists, as well as biochemists, molecular biologists, and other
biologists, simply could not believe this simple result. We proposed that the
variable regions of antibody light and heavy chains would fold together with
these six short segments on one side of this globular structure forming the
antibody combining site. These segments were thus designed as
complementarity determining regions (CDR's). Similar to what the
enzymologists had proposed for the binding of enzyme molecules with their
substrates in a lock-key configuration, we proposed the same for antibodies
binding antigens. Furthermore, various combinations of these six “fingers”
could easily generate the required number of millions or billions of different
antibodies. Using the Kabat numbering system, we specify the positions for
the six CDR's as listed in Table 1-1. Other portions of the variable region
are designated as framework regions (FR's). Slight variations are observed
in some species.
Table 1-1. Positions for FR's and CDR's of light and heavy chains of antibodies (modified
from Kabat
et al
., 1991).
Segment
Light Chain
Heavy Chain
FR1
1-23 (with occasional 0, and
deletion of 10 in
1-30 (with occasional 0)
CDR1
24-34 (with possible insertions
between 27 and 28)
31-35 (with possible insertions
between 35 and 36)
FR2
35-49
36-49
CDR2
50-56
50-65 (with possible insertions
between 52 and 53)
66-94 (with possible insertions
between 82 and 83)
FR3
57-88
CDR3
89-97 (with possible insertions
between 95 and 96)
95-102 (with possible insertions
between 100 and 101)
FR4
98-107 (with possible extra
residue after 106)
103-113
