Chemicals and Drugs

Complement C1s

A 77-kDa subcomponent of complement C1, encoded by gene C1S, is a SERINE PROTEASE existing as a proenzyme (homodimer) in the intact complement C1 complex. Upon the binding of COMPLEMENT C1Q to antibodies, the activated COMPLEMENT C1R cleaves C1s into two chains, A (heavy) and B (light, the serine protease), linked by disulfide bonds yielding the active C1s. The activated C1s, in turn, cleaves COMPLEMENT C2 and COMPLEMENT C4 to form C4b2a (CLASSICAL C3 CONVERTASE).

National Library of MedicineMedical Subject Headings2026

Structured Summary

Abstract

A 77-kDa subcomponent of complement C1, encoded by gene C1S, is a SERINE PROTEASE existing as a proenzyme (homodimer) in the intact complement C1 complex. Upon the binding of COMPLEMENT C1Q to antibodies, the activated COMPLEMENT C1R cleaves C1s into two chains, A (heavy) and B (light, the serine protease), linked by disulfide bonds yielding the active C1s. The activated C1s, in turn, cleaves COMPLEMENT C2 and COMPLEMENT C4 to form C4b2a (CLASSICAL C3 CONVERTASE).

MeSH Record

Classification

Related Concepts

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Drug Class

Pharmacological Action

MeSH Record

Synonyms

12 entry terms
  • C 1 Esterase
  • C1 Esterase
  • C1s Complement
  • Complement 1 Esterase
  • Complement 1s
  • Complement Component 1s
  • C1s, Complement
  • Complement, C1s
  • Component 1s, Complement
  • Esterase, C 1
  • Esterase, C1
  • Esterase, Complement 1

MeSH Record

Aspects Covered

29 allowable subheadings

Indexed with the subheadings administration & dosage, adverse effects, agonists, analysis, antagonists & inhibitors, biosynthesis, cerebrospinal fluid, chemical synthesis, chemistry, classification, deficiency, drug effects, economics, genetics, history, immunology, isolation & purification, metabolism, pharmacokinetics, pharmacology, physiology, poisoning, radiation effects, standards, supply & distribution, therapeutic use, toxicity, ultrastructure, urine.

MeSH Record

History Note

2006 (1978)

MeSH Record

Previous Indexing

  • Complement 1 (1975-1977)
  • Esterases (1966-1977)

MeSH Hierarchy

Tree Numbers

AMA Style

References

  1. National Library of Medicine. Complement C1s. Medical Subject Headings (MeSH). 2026. Unique ID D003173. http://id.nlm.nih.gov/mesh/2026/D003173
  2. Complement C1s. In: Wikidata. https://www.wikidata.org/wiki/Q21111743