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Reviewed, UniProtKB/Swiss-Prot P09871 (C1S_HUMAN)

Last modified November 4, 2008. Version 123. Feed History...

Clusters with 100%, 90%, 50% identity | Documents (8) | Third-party data | Customize display text xml rdf/xml gff fasta
Names and origin · Protein attributes · General annotation (Comments) · Ontologies · Sequence annotation (Features) · Sequences · References · Web resources · Cross-references · Entry information · Relevant documents

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Names and origin

Protein namesRecommended name:
    Complement C1s subcomponent
    EC=3.4.21.42
Alternative name(s):
    C1 esterase
Cleaved into the following 2 chains:
    1- Recommended name:
            Complement C1s subcomponent heavy chain
    2- Recommended name:
            Complement C1s subcomponent light chain
Gene names
Name: C1S
OrganismHomo sapiens (Human)
Taxonomic identifier9606 [NCBI]
Taxonomic lineageEukaryota › Metazoa › Chordata › Craniata › Vertebrata › Euteleostomi › Mammalia › Eutheria › Euarchontoglires › Primates › Haplorrhini › Catarrhini › Hominidae › Homo

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Protein attributes

Sequence length688 AA.
Sequence statusComplete.
Sequence processingThe displayed sequence is further processed into a mature form.
Protein existenceEvidence at protein level.

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General annotation (Comments)

Function

C1s B chain is a serine protease that combines with C1q and C1s to form C1, the first component of the classical pathway of the complement system. C1r activates C1s so that it can, in turn, activate C2 and C4.

Catalytic activity

Cleavage of Arg-|-Ala bond in complement component C4 to form C4a and C4b, and Lys(or Arg)-|-Lys bond in complement component C2 to form C2a and C2b: the 'classical' pathway C3 convertase.

Subunit structure

C1 is a calcium-dependent trimolecular complex of C1q, C1r and C1s in the molar ration of 1:2:2. Activated C1s is an disulfide-linked heterodimer of a heavy chain and a light chain.

Involvement in disease

Defects in C1S are the cause of selective C1s deficiency [MIM:120580]; that is associated with early onset multiple autoimmune diseases.

Sequence similarities

Belongs to the peptidase S1 family.

Contains 2 CUB domains.

Contains 1 EGF-like domain.

Contains 1 peptidase S1 domain.

Contains 2 Sushi (CCP/SCR) domains.

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Ontologies

Keywords

   Biological processComplement pathway
Immune response
Innate immunity
   Coding sequence diversityPolymorphism
   DomainEGF-like domain
Repeat
Signal
Sushi
   LigandCalcium
Metal-binding
   Molecular functionHydrolase
Protease
Serine protease
   PTMGlycoprotein
Hydroxylation
   Technical term3D-structure
Direct protein sequencing

Gene Ontology (GO)

   Cellular componentextracellular region

Inferred from Experiment. Source: Reactome

   Molecular functionserine-type endopeptidase activity

Traceable author statement. Source: ProtInc

Complete GO annotation...

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Sequence annotation (Features)

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifier

Molecule processing

Signal peptide1 – 1515
Chain16 – 688673Complement C1s subcomponent
PRO_0000027586
Chain16 – 437422Complement C1s subcomponent heavy chain
PRO_0000027587
Chain438 – 688251Complement C1s subcomponent light chain
PRO_0000027588

Regions

Domain16 – 130115CUB 1
Domain131 – 17242EGF-like; calcium-binding
Domain175 – 290116CUB 2
Domain292 – 35665Sushi 1
Domain357 – 42367Sushi 2
Domain438 – 680243Peptidase S1

Sites

Active site4751Charge relay system
Active site5291Charge relay system
Active site6321Charge relay system
Metal binding601Calcium
Metal binding681Calcium
Metal binding1131Calcium
Metal binding1311Calcium
Metal binding1321Calcium; via carbonyl oxygen
Metal binding1341Calcium
Metal binding1491Calcium
Metal binding1501Calcium; via carbonyl oxygen
Metal binding1531Calcium; via carbonyl oxygen

Amino acid modifications

Modified residue14913-hydroxyasparagine; partial
Glycosylation1741N-linked (GlcNAc...)
Glycosylation4061N-linked (GlcNAc...)
Disulfide bond65 ↔ 83
Disulfide bond135 ↔ 147
Disulfide bond143 ↔ 156
Disulfide bond158 ↔ 171
Disulfide bond175 ↔ 202
Disulfide bond234 ↔ 251
Disulfide bond294 ↔ 341
Disulfide bond321 ↔ 354
Disulfide bond359 ↔ 403
Disulfide bond386 ↔ 421
Disulfide bond425 ↔ 549Interchain (between heavy and light chains)
Disulfide bond595 ↔ 618
Disulfide bond628 ↔ 659

Natural variations

Natural variant1191R → H: dbSNP rs12146727.
VAR_033643
Natural variant3271V → L: dbSNP rs2239170.
VAR_033644
Natural variant3831R → H: dbSNP rs20573.
VAR_014565

Experimental info

Sequence conflict2941C → K AA sequence Ref.7
Sequence conflict5131G → GG Ref.6
Sequence conflict5731T → A AA sequence Ref.8
Sequence conflict645 – 6462TK → GR AA sequence Ref.8

Secondary structure

1 ......................................................................... 688
Helix Strand Turn

Details...

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Sequences

Sequence LengthMass (Da)Tools
P09871-1 [UniParc].

Last modified July 1, 1989. Version 1.
Checksum: 85522647A4C47205

FASTA68876,684
        10         20         30         40         50         60 
MWCIVLFSLL AWVYAEPTMY GEILSPNYPQ AYPSEVEKSW DIEVPEGYGI HLYFTHLDIE 

        70         80         90        100        110        120 
LSENCAYDSV QIISGDTEEG RLCGQRSSNN PHSPIVEEFQ VPYNKLQVIF KSDFSNEERF 

       130        140        150        160        170        180 
TGFAAYYVAT DINECTDFVD VPCSHFCNNF IGGYFCSCPP EYFLHDDMKN CGVNCSGDVF 

       190        200        210        220        230        240 
TALIGEIASP NYPKPYPENS RCEYQIRLEK GFQVVVTLRR EDFDVEAADS AGNCLDSLVF 

       250        260        270        280        290        300 
VAGDRQFGPY CGHGFPGPLN IETKSNALDI IFQTDLTGQK KGWKLRYHGD PMPCPKEDTP 

       310        320        330        340        350        360 
NSVWEPAKAK YVFRDVVQIT CLDGFEVVEG RVGATSFYST CQSNGKWSNS KLKCQPVDCG 

       370        380        390        400        410        420 
IPESIENGKV EDPESTLFGS VIRYTCEEPY YYMENGGGGE YHCAGNGSWV NEVLGPELPK 

       430        440        450        460        470        480 
CVPVCGVPRE PFEEKQRIIG GSDADIKNFP WQVFFDNPWA GGALINEYWV LTAAHVVEGN 

       490        500        510        520        530        540 
REPTMYVGST SVQTSRLAKS KMLTPEHVFI HPGWKLLEVP EGRTNFDNDI ALVRLKDPVK 

       550        560        570        580        590        600 
MGPTVSPICL PGTSSDYNLM DGDLGLISGW GRTEKRDRAV RLKAARLPVA PLRKCKEVKV 

       610        620        630        640        650        660 
EKPTADAEAY VFTPNMICAG GEKGMDSCKG DSGGAFAVQD PNDKTKFYAA GLVSWGPQCG 

       670        680 
TYGLYTRVKN YVDWIMKTMQ ENSTPRED

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References

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[1]"Molecular cloning of cDNA for human complement component C1s. The complete amino acid sequence."