Lysines and cysteines of the Homo sapiens IGHG1, IGKC and IGLC1 and positions in the C-DOMAIN

Positions are according to the IMGT unique numbering for C-DOMAIN [1]. For correspondence between the IMGT unique numbering with other numberings, see Correspondence between C numberings.

In addition to the lysines are shown:
- the five characteristic amino acids of a C-DOMAIN [2,3]. Four of them are highly conserved and hydrophobic [4] and are common to the V domain: C23 (1st-CYS), W41 (CONSERVED-TRP), 89 (hydrophobic) and C104 (2nd-CYS) [5]. These four amino acids contribute to the two major features shared by the V and C domains: the disulfide bridge (between the two cysteines 23 and 104) and the internal hydrophobic core of the domain (with the side chains of tryptophan W41 and amino acid 89) [2,3]. The fifth position, 118 is diverse in the C-DOMAIN and is characterized as being an FG loop anchor (whereas it is conserved in the V-DOMAIN and represented by J-PHE 118 or J-TRP 118).
- the CH2 N84.4 site of N-glycosylation (IMGT Lexique Glycosylation) at the top of the DE turn. The asparagine N84.4 is part of a N-glycosylation motif NXS/T (NST in Homo sapiens IGHG1).

References:

[1]	Lefranc, M.-P., Pommié, C., Kaas, Q., Duprat, E., Bosc, N., Guiraudou, D., Jean, C., Ruiz, M., Da Piedade, I., Rouard, M., Foulquier, E., Thouvenin, V. and Lefranc, G. IMGT unique numbering for immunoglobulin and T cell receptor constant domains and Ig superfamily C-like domains. Dev. Comp. Immunol., 29, 185-203 (2005).PMID: 15572068 with permission from Elsevier.
[2]	Lefranc, M-P. Immunoglobulin (IG) and T cell receptor genes (TR): IMGT® and the birth and rise of immunoinformatics. Front Immunol. 2014 Feb 05;5:22. doi: 10.3389/fimmu.2014.00022. Open access. PMID: 24600447.
[3]	Lefranc, M-P. Immunoglobulins: 25 years of Immunoinformatics and IMGT-ONTOLOGY. Biomolecules. 2014, 4(4), 1102-1139; doi:10.3390/biom4041102. Open access. PMID: 25521638.
[4]	Pommié, C., Levadoux, S., Sabatier, R., Lefranc, G. and Lefranc, M.-P. IMGT standardized criteria for statistical analysis of immunoglobulin V-REGION amino acid properties J. Mol. Recognit., 17, 17-32 (2004). PMID: 14872534 .
[5]	Lefranc, M.-P., Pommié, C., Ruiz, M., Giudicelli, V., Foulquier, E., Truong, L., Thouvenin-Contet, V. and Lefranc, G. IMGT unique numbering for immunoglobulin and T cell receptor variable domains and Ig superfamily V-like domains. Dev. Comp. Immunol., 27, 55-77 (2003). PMID: 12477501 with permission from Elsevier.