X-group (possible homology)

233 MHC antigen-recognition domain

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Ligands and drugs

4,020

Member domains

1,716

with ligand contacts (≤ 4 Å)

42.7% of members

1,490

with DrugDomain annotations

37.1% of members

1,202

with a DrugBank compound

29.9% of members

Aggregated over all current member domains of this group. Drug annotations come from DrugDomain; buffers and crystallization additives are excluded from the tables below.

Chemical profile

ClassyFire chemical superclasses of the ligands bound by this X-group's proteins, from DrugDomain annotations.

129

Proteins with classified ligands

Superclasses bound (of 23)

8.1

Superclasses per 20 proteins

broader than 60% of the 256 X-groups with enough proteins to compare (median 7.6)

The raw number of superclasses rises with the number of proteins sampled; the per-20 value compares X-groups at equal depth.

Superclass	Proteins	Expected	Ratio	Significance
Organic oxygen compounds	94	25.3	3.71×	q < 0.0001
Lipids and lipid-like molecules	16	14.2	1.13×	q = 0.65
Homogeneous non-metal compounds	29	27.4	1.06×	q = 0.81
Organic acids and derivatives	14	19.7	0.71×	q = 0.24
Homogeneous metal compounds	39	62.4	0.63×	q = 1.0e-4
Benzenoids	3	9.3	0.32×	q = 0.04
Organoheterocyclic compounds	5	19.6	0.26×	q = 2.1e-4
Nucleosides, nucleotides, and analogues	1	35.2	0.03×	q < 0.0001
Hydrocarbons	5	0.9	5.63×	not tested
Organic nitrogen compounds	9	4.1	2.22×	not tested
Organosulfur compounds	5	2.6	1.91×	not tested
Mixed metal/non-metal compounds	1	2.7	0.37×	not tested

enriched (q < 0.05)depleted (q < 0.05)not significantnot tested (expected < 5)

Unit: a protein (UniProt accession) with a ligand-binding domain in this X-group, counted once per superclass. Expected counts use each superclass's frequency across all ligand-binding X-groups; significance is Fisher's exact test with Benjamini–Hochberg correction. Buffers and crystallization additives are excluded. ECOD v295.2; the method follows the ECOD 2027 update, whose published figures used a slightly different artifact filter.

DrugBank compounds

DrugBank	PDB ligand	Name	Domains
DB00141	NAG	N-Acetylglucosamine	478
DB03796	PLM	Palmitic Acid	31
DB12232	AGH	Alpha-galactosylceramide	17
DB04661	CIS	cis-tetracosenoyl sulfatide	9
DB00145	GLY	Glycine	8
DB01048	1KX	Abacavir	7
DB02676	B3P	2-[3-(2-Hydroxy-1,1-Dihydroxymethyl-Ethylamino)-Propylamino]-2-Hydroxymethyl-Propane-1,3-Diol	7
DB00151	CYS	Cysteine	6
DB04473	FUC	alpha-L-fucose	6
DB00125	ARG	Arginine	5
DB00149	LEU	Leucine	5
DB02175	MLA	Malonic acid	5
DB03309	NHE	N-cyclohexyltaurine	5
DB03345	BME	Mercaptoethanol	5
DB00134	MET	Methionine	3
DB08231	MYR	Myristic acid	3
DB08357	P4G	Diethylene glycol diethyl ether	3
DB00586	DIF	Diclofenac	2
DB00847	DHL	Cysteamine	2
DB02144	PIE	1,2-diacyl-sn-glycero-3-phosphoinositol	2

Most frequently bound compounds

PDB ligand	Name	Domains in contact
NAG	2-acetamido-2-deoxy-beta-D-glucopyranose	513
CL	CHLORIDE ION	101
NAmetal	SODIUM ION	91
ZNmetal	ZINC ION	37
PLM	PALMITIC ACID	31
2LJ	1-deoxy-1-({2,6-dioxo-5-[(E)-propylideneamino]-1,2,3,6-tetrahydropyrimidin-4-yl}amino)-D-ribitol	30
IOD	IODIDE ION	30
MGmetal	MAGNESIUM ION	27
30W	N-(6-formyl-4-oxo-3,4-dihydropteridin-2-yl)acetamide	21
PTY	PHOSPHATIDYLETHANOLAMINE	20
CAmetal	CALCIUM ION	18
AGH	N-{(1S,2R,3S)-1-[(ALPHA-D-GALACTOPYRANOSYLOXY)METHYL]-2,3-DIHYDROXYHEPTADECYL}HEXACOSANAMIDE	17
CDmetal	CADMIUM ION	17
Q87	1-deoxy-1-({2,6-dioxo-5-[(E)-(2-oxopropylidene)amino]-1,2,3,6-tetrahydropyrimidin-4-yl}amino)-D-ribitol	12
D12	DODECANE	11
CUY	tetracosyl octadecanoate	10
CIS	(15Z)-N-((1S,2R,3E)-2-HYDROXY-1-{[(3-O-SULFO-BETA-D-GALACTOPYRANOSYL)OXY]METHYL}HEPTADEC-3-ENYL)TETRACOS-15-ENAMIDE	9
EKG	(2R)-2,3-dihydroxypropyl hexadecanoate	9
GLY	GLYCINE	8
MYR	MYRISTIC ACID	8