Complement component 1s

Complement component 1s (EC, C1 esterase, activated complement C1s, complement C overbar 1r, C1s) is a protein involved in the complement system. C1s is part of the C1 complex.[5][6][7][8] In humans, it is encoded by the C1S gene.[9]

Available structures
PDBOrtholog search: PDBe RCSB
AliasesC1S, EDSPD2, complement C1s
External IDsOMIM: 120580 MGI: 3644269 HomoloGene: 1314 GeneCards: C1S
EC number3.4.21.42
Gene location (Human)
Chr.Chromosome 12 (human)[1]
Band12p13.31Start6,988,259 bp[1]
End7,071,032 bp[1]
RNA expression pattern
More reference expression data









RefSeq (mRNA)



RefSeq (protein)



Location (UCSC)Chr 12: 6.99 – 7.07 MbChr 6: 124.62 – 124.64 Mb
PubMed search[3][4]
View/Edit HumanView/Edit Mouse

C1s cleaves C4 and C2, which eventually leads to the production of the classical pathway C3-convertase.

Classical pathway. (Some labels are in Polish.)

See also

  • C1q - another part of the C1 complex
  • C1r - another part of the C1 complex
  • MASP-2 - a protein similar to C1s, part of the lectin pathway


  1. GRCh38: Ensembl release 89: ENSG00000182326 - Ensembl, May 2017
  2. GRCm38: Ensembl release 89: ENSMUSG00000079343 - Ensembl, May 2017
  3. "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  4. "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  5. Sim RB (1981). "The human complement system serine proteases C1r and C1s and their proenzymes". Methods in Enzymology. 80 Pt C: 26–42. doi:10.1016/s0076-6879(81)80006-7. PMID 6281620.
  6. Mackinnon CM, Carter PE, Smyth SJ, Dunbar B, Fothergill JE (December 1987). "Molecular cloning of cDNA for human complement component C1s. The complete amino acid sequence". European Journal of Biochemistry. 169 (3): 547–53. doi:10.1111/j.1432-1033.1987.tb13644.x. PMID 3500856.
  7. Müller-Eberhard HJ (1988). "Molecular organization and function of the complement system". Annual Review of Biochemistry. 57: 321–47. doi:10.1146/ PMID 3052276.
  8. Skoog MT, Mehdi S, Wiseman JS, Bey P (June 1989). "The specificity of two proteinases that cleave adjacent to arginine, C1 esterase and acrosin, for peptide p-nitroanilide substrates". Biochimica et Biophysica Acta. 996 (1–2): 89–94. doi:10.1016/0167-4838(89)90099-x. PMID 2500154.
  9. "Entrez Gene: C1S Complement component 1, s subcomponent".

Further reading

  • Luo C, Thielens NM, Gagnon J, Gal P, Sarvari M, Tseng Y, Tosi M, Zavodszky P, Arlaud GJ, Schumaker VN (May 1992). "Recombinant human complement subcomponent C1s lacking beta-hydroxyasparagine, sialic acid, and one of its two carbohydrate chains still reassembles with C1q and C1r to form a functional C1 complex". Biochemistry. 31 (17): 4254–62. doi:10.1021/bi00132a015. PMID 1533159.
  • Illy C, Thielens NM, Gagnon J, Arlaud GJ (July 1991). "Effect of lactoperoxidase-catalyzed iodination on the Ca(2+)-dependent interactions of human C1s. Location of the iodination sites". Biochemistry. 30 (29): 7135–41. doi:10.1021/bi00243a014. PMID 1854725.
  • Hess D, Schaller J, Rickli EE (March 1991). "Identification of the disulfide bonds of human complement C1s". Biochemistry. 30 (11): 2827–33. doi:10.1021/bi00225a014. PMID 2007122.
  • Thielens NM, Van Dorsselaer A, Gagnon J, Arlaud GJ (April 1990). "Chemical and functional characterization of a fragment of C1-s containing the epidermal growth factor homology region". Biochemistry. 29 (14): 3570–8. doi:10.1021/bi00466a021. PMID 2141278.
  • Busby TF, Ingham KC (May 1990). "NH2-terminal calcium-binding domain of human complement C1s- mediates the interaction of C1r- with C1q". Biochemistry. 29 (19): 4613–8. doi:10.1021/bi00471a016. PMID 2372546.
  • Kusumoto H, Hirosawa S, Salier JP, Hagen FS, Kurachi K (October 1988). "Human genes for complement components C1r and C1s in a close tail-to-tail arrangement". Proceedings of the National Academy of Sciences of the United States of America. 85 (19): 7307–11. doi:10.1073/pnas.85.19.7307. PMC 282175. PMID 2459702.
  • Katz Y, Strunk RC (March 1989). "Synthesis and regulation of C1 inhibitor in human skin fibroblasts". Journal of Immunology. 142 (6): 2041–5. PMID 2537870.
  • Tosi M, Duponchel C, Meo T, Couture-Tosi E (August 1989). "Complement genes C1r and C1s feature an intronless serine protease domain closely related to haptoglobin". Journal of Molecular Biology. 208 (4): 709–14. doi:10.1016/0022-2836(89)90161-7. PMID 2553984.
  • Tosi M, Duponchel C, Meo T, Julier C (December 1987). "Complete cDNA sequence of human complement Cls and close physical linkage of the homologous genes Cls and Clr". Biochemistry. 26 (26): 8516–24. doi:10.1021/bi00400a004. PMID 2831944.
  • Nguyen VC, Tosi M, Gross MS, Cohen-Haguenauer O, Jegou-Foubert C, de Tand MF, Meo T, Frézal J (April 1988). "Assignment of the complement serine protease genes C1r and C1s to chromosome 12 region 12p13". Human Genetics. 78 (4): 363–8. doi:10.1007/BF00291737. PMID 2834284.
  • Spycher SE, Nick H, Rickli EE (April 1986). "Human complement component C1s. Partial sequence determination of the heavy chain and identification of the peptide bond cleaved during activation". European Journal of Biochemistry. 156 (1): 49–57. doi:10.1111/j.1432-1033.1986.tb09546.x. PMID 3007145.
  • Mackinnon CM, Carter PE, Smyth SJ, Dunbar B, Fothergill JE (December 1987). "Molecular cloning of cDNA for human complement component C1s. The complete amino acid sequence". European Journal of Biochemistry. 169 (3): 547–53. doi:10.1111/j.1432-1033.1987.tb13644.x. PMID 3500856.
  • Kauffman D, Hofmann T, Bennick A, Keller P (May 1986). "Basic proline-rich proteins from human parotid saliva: complete covalent structures of proteins IB-1 and IB-6". Biochemistry. 25 (9): 2387–92. doi:10.1021/bi00357a013. PMID 3521730.
  • Bock SC, Skriver K, Nielsen E, Thøgersen HC, Wiman B, Donaldson VH, Eddy RL, Marrinan J, Radziejewska E, Huber R (July 1986). "Human C1 inhibitor: primary structure, cDNA cloning, and chromosomal localization". Biochemistry. 25 (15): 4292–301. doi:10.1021/bi00363a018. PMID 3756141.
  • Carter PE, Dunbar B, Fothergill JE (December 1983). "The serine proteinase chain of human complement component C1s. Cyanogen bromide cleavage and N-terminal sequences of the fragments". The Biochemical Journal. 215 (3): 565–71. doi:10.1042/bj2150565. PMC 1152437. PMID 6362661.
  • Nilsson T, Sjöholm I, Wiman B (September 1983). "Structural and circular-dichroism studies on the interaction between human C1-esterase inhibitor and C1s". The Biochemical Journal. 213 (3): 617–24. doi:10.1042/bj2130617. PMC 1152176. PMID 6604523.
  • Rossi V, Gaboriaud C, Lacroix M, Ulrich J, Fontecilla-Camps JC, Gagnon J, Arlaud GJ (June 1995). "Structure of the catalytic region of human complement protease C1s: study by chemical cross-linking and three-dimensional homology modeling". Biochemistry. 34 (22): 7311–21. doi:10.1021/bi00022a004. PMID 7779774.
  • Bersch B, Hernandez JF, Marion D, Arlaud GJ (February 1998). "Solution structure of the epidermal growth factor (EGF)-like module of human complement protease C1r, an atypical member of the EGF family". Biochemistry. 37 (5): 1204–14. doi:10.1021/bi971851v. PMID 9477945.
  • Endo Y, Takahashi M, Nakao M, Saiga H, Sekine H, Matsushita M, Nonaka M, Fujita T (November 1998). "Two lineages of mannose-binding lectin-associated serine protease (MASP) in vertebrates". Journal of Immunology. 161 (9): 4924–30. PMID 9794427.
  • Inoue N, Saito T, Masuda R, Suzuki Y, Ohtomi M, Sakiyama H (October 1998). "Selective complement C1s deficiency caused by homozygous four-base deletion in the C1s gene". Human Genetics. 103 (4): 415–8. doi:10.1007/s004390050843. PMID 9856483.
  • Complement+C1s at the US National Library of Medicine Medical Subject Headings (MeSH)
  • Human C1S genome location and C1S gene details page in the UCSC Genome Browser.

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