Antibody CDR annotation

Find the CDRs and FRs in an protein sequence. If you want to numbering an antibody please visit Antibody Sequence Numbering

1. Input a single protein(raw sequence):

Full Length:0

2. Select a numbering scheme:

3. Select a definition scheme:

Table of CDR Definitions

The Kabat definition is based on sequence variability and is the most commonly used

The Chothia definition is based on the location of the structural loop regions

The contact definition has been recently introduced by us and is based on an analysis of the available complex crystal structures. This definition is likely to be the most useful for people wishing to perform mutagenesis to modify the afinity of an antibody since these are residues which take part in interactions with antigen. Lists of CDR residues making contact in each antibody with summary data for each CDR

Loop Kabat AbM Chothia1 Contact2 IMGT
L1 L24--L34 L24--L34 L24--L34 L30--L36 L27--L32
L2 L50--L56 L50--L56 L50--L56 L46--L55 L50--L51
L3 L89--L97 L89--L97 L89--L97 L89--L96 L89--L97
H1 H31--H35B
(Kabat Numbering)3
H26--H35B H26--H32..34 H30--H35B H26--H35B
H1 H31--H35
(Chothia Numbering)
H26--H35 H26--H32 H30--H35 H26--H33
H2 H50--H65 H50--H58 H52--H56 H47--H58 H51--H56
H3 H95--H102 H95--H102 H95--H102 H93--H101 H93--H102

Note (1) some of these definitions (particularly for Chothia loops) vary depending on the individual publication examined.

Note (2) any of the numbering schemes can be used for these CDR defintions, except the contact definition uses the Chothia or Martin (Enhanced Chothia) definition.

Note (3) the end of the Chothia CDR-H1 loop when numbered using the Kabat numbering convention varies between H32 and H34 depending on the length of the loop. (This is because the Kabat numbering scheme places the insertions at H35A and H35B.). If neither H35A nor H35B is present, the loop ends at H32; If only H35A is present, the loop ends at H33; If both H35A and H35B are present, the loop ends at H34.