Complement component 1r

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RefSeq (mRNA)



RefSeq (protein)



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Complement C1r subcomponent (EC, activated complement C1r, C overbar 1r esterase, C1r) is a protein involved in the complement system of the innate immune system.[1][2][3] In humans, C1r is encoded by the C1R gene.[4]

C1r along with C1q and C1s form the C1 complex, which is the first component of the serum complement system. C1r is an enzyme that activates C1s to its active form, by proteolytic cleavage.


C1r has been shown to interact with C1s. C1r cleaves C1s to form the active form of C1s.[5][6]


  1. 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.
  2. Leytus SP, Kurachi K, Sakariassen KS, Davie EW (August 1986). "Nucleotide sequence of the cDNA coding for human complement C1r". Biochemistry. 25 (17): 4855–63. doi:10.1021/bi00365a020. PMID 3021205.
  3. Müller-Eberhard HJ (1988). "Molecular organization and function of the complement system". Annual Review of Biochemistry. 57: 321–47. doi:10.1146/ PMID 3052276.
  4. "Entrez Gene: C1R complement component 1, r subcomponent".
  5. Thielens NM, Enrie K, Lacroix M, Jaquinod M, Hernandez JF, Esser AF, Arlaud GJ (April 1999). "The N-terminal CUB-epidermal growth factor module pair of human complement protease C1r binds Ca2+ with high affinity and mediates Ca2+-dependent interaction with C1s". The Journal of Biological Chemistry. 274 (14): 9149–59. doi:10.1074/jbc.274.14.9149. PMID 10092586.
  6. Thiel S, Petersen SV, Vorup-Jensen T, Matsushita M, Fujita T, Stover CM, Schwaeble WJ, Jensenius JC (July 2000). "Interaction of C1q and mannan-binding lectin (MBL) with C1r, C1s, MBL-associated serine proteases 1 and 2, and the MBL-associated protein MAp19". Journal of Immunology. 165 (2): 878–87. doi:10.4049/jimmunol.165.2.878. PMID 10878362.

Further reading

  • Lee SL, Wallace SL, Barone R, Blum L, Chase PH (1979). "Familial deficiency of two subunits of the first component of complement. C1r and C1s associated with a lupus erythematosus-like disease". Arthritis and Rheumatism. 21 (8): 958–67. doi:10.1002/art.1780210813. PMID 737019.
  • Ward SL, Ingham KC (January 1992). "A calcium-binding monoclonal antibody that recognizes a non-calcium-binding epitope in the short consensus repeat units (SCRs) of complement C1r". Molecular Immunology. 29 (1): 83–93. doi:10.1016/0161-5890(92)90160-Y. PMID 1370572.
  • 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.
  • 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.
  • Lyons LA, Kamboh MI, Ferrell RE (1989). "Genetic studies of low-abundance human plasma proteins. XI. Linkage analysis and population genetics of the C1S subcomponent of the first complement component". Complement and Inflammation. 6 (2): 81–7. PMID 2541966.
  • Arlaud GJ, Van Dorsselaer A, Bell A, Mancini M, Aude C, Gagnon J (September 1987). "Identification of erythro-beta-hydroxyasparagine in the EGF-like domain of human C1r". FEBS Letters. 222 (1): 129–34. doi:10.1016/0014-5793(87)80205-3. PMID 2820791.
  • 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.
  • Leytus SP, Kurachi K, Sakariassen KS, Davie EW (August 1986). "Nucleotide sequence of the cDNA coding for human complement C1r". Biochemistry. 25 (17): 4855–63. doi:10.1021/bi00365a020. PMID 3021205.
  • Journet A, Tosi M (December 1986). "Cloning and sequencing of full-length cDNA encoding the precursor of human complement component C1r". The Biochemical Journal. 240 (3): 783–7. PMC 1147487. PMID 3030286.
  • Arlaud GJ, Willis AC, Gagnon J (February 1987). "Complete amino acid sequence of the A chain of human complement-classical-pathway enzyme C1r". The Biochemical Journal. 241 (3): 711–20. PMC 1147622. PMID 3036070.
  • Chesne S, Villiers CL, Arlaud GJ, Lacroix MB, Colomb MG (January 1982). "Fluid-phase interaction of C1 inhibitor (C1 Inh) and the subcomponents C1r and C1s of the first component of complement, C1". The Biochemical Journal. 201 (1): 61–70. PMC 1163609. PMID 6282262.
  • Arlaud GJ, Gagnon J (April 1983). "Complete amino acid sequence of the catalytic chain of human complement subcomponent C1-r". Biochemistry. 22 (8): 1758–64. doi:10.1021/bi00277a003. PMID 6303394.
  • Maruyama K, Sugano S (January 1994). "Oligo-capping: a simple method to replace the cap structure of eukaryotic mRNAs with oligoribonucleotides". Gene. 138 (1–2): 171–4. doi:10.1016/0378-1119(94)90802-8. PMID 8125298.
  • Nöthen MM, Dewald G (January 1994). "A common amino acid polymorphism in complement component C1R". Human Molecular Genetics. 3 (1): 217. doi:10.1093/hmg/3.1.217-a. PMID 8162045.
  • Gasque P, Ischenko A, Legoedec J, Mauger C, Schouft MT, Fontaine M (November 1993). "Expression of the complement classical pathway by human glioma in culture. A model for complement expression by nerve cells". The Journal of Biological Chemistry. 268 (33): 25068–74. PMID 8227070.
  • Pelloux S, Thielens NM, Hudry-Clergeon G, Pétillot Y, Filhol O, Arlaud GJ (May 1996). "Identification of a cryptic protein kinase CK2 phosphorylation site in human complement protease Clr, and its use to probe intramolecular interaction". FEBS Letters. 386 (1): 15–20. doi:10.1016/0014-5793(96)00403-6. PMID 8635594.
  • Bradley K, North J, Saunders D, Schwaeble W, Jeziorska M, Woolley DE, Whaley K (August 1996). "Synthesis of classical pathway complement components by chondrocytes". Immunology. 88 (4): 648–56. PMC 1456645. PMID 8881771.
  • Lacroix M, Rossi V, Gaboriaud C, Chevallier S, Jaquinod M, Thielens NM, Gagnon J, Arlaud GJ (May 1997). "Structure and assembly of the catalytic region of human complement protease C1r: a three-dimensional model based on chemical cross-linking and homology modeling". Biochemistry. 36 (21): 6270–82. doi:10.1021/bi962719i. PMID 9174342.
  • Suzuki Y, Yoshitomo-Nakagawa K, Maruyama K, Suyama A, Sugano S (October 1997). "Construction and characterization of a full length-enriched and a 5'-end-enriched cDNA library". Gene. 200 (1–2): 149–56. doi:10.1016/S0378-1119(97)00411-3. PMID 9373149.
  • 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.

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