X-group (possible homology)

243 Cystatin-like

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Ligands and drugs

8,478

Member domains

1,822

with ligand contacts (≤ 4 Å)

21.5% of members

1,427

with DrugDomain annotations

16.8% of members

898

with a DrugBank compound

10.6% 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.

152

Proteins with classified ligands

Superclasses bound (of 23)

8.3

Superclasses per 20 proteins

broader than 62% 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
Homogeneous non-metal compounds	57	32.3	1.77×	q < 0.0001
Benzenoids	17	11.0	1.55×	q = 0.12
Lipids and lipid-like molecules	20	16.7	1.20×	q = 0.44
Homogeneous metal compounds	66	73.6	0.90×	q = 0.29
Organic oxygen compounds	23	29.8	0.77×	q = 0.25
Organic acids and derivatives	17	23.2	0.73×	q = 0.24
Organoheterocyclic compounds	12	23.1	0.52×	q = 0.02
Nucleosides, nucleotides, and analogues	1	41.4	0.02×	q < 0.0001
Organic nitrogen compounds	7	4.8	1.46×	not tested
Organosulfur compounds	4	3.1	1.30×	not tested
Phenylpropanoids and polyketides	2	3.1	0.64×	not tested
Mixed metal/non-metal compounds	2	3.2	0.64×	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
DB18267	HEM	Ferroheme	94
DB03515	EQU	Equilenin	62
DB00141	NAG	N-Acetylglucosamine	54
DB02178	HY1	Phenylacetaldehyde	24
DB03671	DOG	Digoxigenin	13
DB01536	ASD	Androstenedione	10
DB00161	VAL	Valine	8
DB00766	J01	Clavulanic acid	6
DB02464	ABN	Benzylamine	6
DB03619	DXC	Deoxycholic acid	6
DB00145	GLY	Glycine	5
DB03175	POL	Propyl alcohol	5
DB03904	URE	Urea	5
DB04064	NGV	Nogalaviketone	5
DB00536	GAI	Guanidine	4
DB01728	PEF	1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine	4
DB02880	BFS	N-[(1R)-1-(4-Bromophenyl)ethyl]-5-fluoro-2-hydroxybenzamide	4
DB02946	CRP	Carpropamide	4
DB03255	IPH	Phenol	4
DB03345	BME	Mercaptoethanol	4

Most frequently bound compounds

PDB ligand	Name	Domains in contact
NAmetal	SODIUM ION	209
CL	CHLORIDE ION	153
CAmetal	CALCIUM ION	122
HEM	PROTOPORPHYRIN IX CONTAINING FE	96
EQU	EQUILENIN	62
CDmetal	CADMIUM ION	48
UNL	Unknown ligand	47
MGmetal	MAGNESIUM ION	41
NAG	2-acetamido-2-deoxy-beta-D-glucopyranose	41
ZNmetal	ZINC ION	34
Kmetal	POTASSIUM ION	25
45D	beta,beta-carotene-4,4'-dione	24
HY1	PHENYLACETALDEHYDE	24
IOD	IODIDE ION	23
ECH	beta,beta-caroten-4-one	18
DOG	DIGOXIGENIN	17
PEA	2-PHENYLETHYLAMINE	16
3ZS	(1R,5S)-6-oxabicyclo[3.1.0]hexane	14
MRD	(4R)-2-METHYLPENTANE-2,4-DIOL	14
CUmetal	COPPER (II) ION	13