C-type lectin

A C-type lectin (CLEC) is a type of carbohydrate-binding protein known as a lectin.^[3] The C-type designation is from their requirement for calcium for binding.^[4] Proteins that contain C-type lectin domains have a diverse range of functions including cell-cell adhesion, immune response to pathogens and apoptosis.^[5][6]

Lectin C-type domain
Pentameric structure of rattlesnake venom lectin which is a galactose binding lectin.[1][2]
Identifiers
Symbol	Lectin_C
Pfam	PF00059
InterPro	IPR001304
SMART	CLECT
PROSITE	PS50041
SCOP2	2msb / SCOPe / SUPFAM
CDD	cd00037
Available protein structures: Pfam   structures / ECOD   PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

Classification

Drickamer et al. classified C-type lectins into 7 subgroups (I to VII) based on the order of the various protein domains in each protein.^[7] This classification was subsequently updated in 2002, leading to seven additional groups (VIII to XIV).^[8] Most recently, three further subgroups were added (XV to XVII).^[3]

Group	Name	Associated domains
I	Lecticans	EGF, Sushi, Ig and Link domains
II	Asialoglycoprotein and DC receptors	None
III	Collectins	None
IV	Selectins	Sushi and EGF domains
V	NK - cell receptors	None
VI	Multi-CTLD endocytic receptors	FnII and Ricin domains
VII	Reg group	None
VIII	Chondrolectin, Layilin	None
IX	Tetranectin	None
X	Polycystin	WSC, REJ, PKD domains
XI	Attractin (ATRN)	PSI, EGF and CUB domains
XII	Eosinophil major basic protein (EMBP)	None
XIII	DGCR2	None
XIV	Thrombomodulin, CD93, CD248, CLEC14A	EGF domains [9]
XV	Bimlec	None
XVI	SEEC	SCP and EGF domains
XVII	CBCP/Frem1/QBRICK	CSPG repeats and CalX-beta domains

CLECs include:

• CLEC1A, CLEC1B
• CLEC2A, CLEC2B, CD69 (CLEC2C), CLEC2D, CLEC2L
• CLEC3A, CLEC3B
• CLEC4A, CLEC4C, CLEC4D, CLEC4E, CLEC4F, CLEC4G, ASGR1 (CLEC4H1), ASGR2 (CLEC4H2), FCER2 (CLEC4J), CD207 (CLEC4K), CD209 (CLEC4L), CLEC4M
• CLEC5A
• CLEC6A
• CLEC7A
• OLR1 (CLEC8A)
• CLEC9A
• CLEC10A
• CLEC11A
• CLEC12A, CLEC12B
• CD302 (CLEC13A), LY75 (CLEC13B), PLA2R1 (CLEC13C), MRC1 (CLEC13D), MRC2 (CLEC13E)
• CLEC14A
• CLEC16A
• CLEC17A

The "NK Cell lectin-like receptors" are a very closely related group:^[10]

• KLRA1
• KLRB1 (CLEC5B)
• KLRC1, KLRC2, KLRC3, KLRC4
• KLRD1
• KLRF1 (CLEC5C)
• KLRG1 (CLEC15A), KLRG2 (CLEC15B)
• KLRK1

Additional proteins containing this domain include:

• AGC1; ATRNL1
• BCAN
• CD248; CD72; CD93; CHODL; CL-K1-Ia; CL-K1-Ib; CL-K1-Ic; CLECSF5; COLEC10; COLEC11; COLEC12; CSPG3
• FCER2; FREM1; HBXBP;
• LAYN; LOC348174; LOC728276
• MAFA; MBL2; MGC34761; MICL; MRC1L1
• OLR1
• PAP; PKD1; PKD1L2; PLA2R1; PRG2; PRG3
• REG1A; REG1B; REG3A; REG3G; REG4
• SELE; SELL; SELP; SFTPA1; SFTPA2; SFTPA2B; SFTPD; SRCL
• THBD
• VCAN