| component of complement | Any one of the nine distinct protein units (designated C1 through C9 and distributed in the a, b, and g electrophoretic partitions of normal serum) that effect the immunological activities long associated with complement. C1 is a complex of three subunits: C1q, C1r, and C1s. C1q (overbar indicates "active form") activates proenzyme C1r to C1r which activates C1s to C1s (also known as C1 esterase), which converts proenzyme C2 to C2b and produces C4b from C4. C2b combines with C4b to form "classical-complement-pathway C3/C5 convertase" (also known as C3 convertase, C5 convertase, and C42). This enzyme cleaves C3 to C3a and C3b, and C5 to yield C5a and C5b, as does "alternative-complement-pathway C3/C5 convertase" (also known as proenzyme factor B, properdin factor B, C3 proactivator, and heat-labile factor). Complement factor I (also known as C3b or C3b/C4b inactivator) inactivates C3b and C4b by a different proteolytic cleavage. Several autosomal recessive disorders have been identified in which one or more of the complement components have been deficient or completely absent. (05 Mar 2000) |
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| component of force | One of the factors from which a resultant force may be compounded or into which it may be resolved, one of the vectors into which a force may be resolved. (05 Mar 2000) |
| component S, glutamate mutase | <chemical> Component s of the coenzyme b12-dependent glutamate mutase from clostridium cochlearium; mw 15 kD; amino acid sequence given in first source Synonym: glms gene product, muts gene product (clostridium) (26 Jun 1999) |
| plasma thromboplastin component | <chemical> Storage-stable blood coagulation factor acting in the intrinsic pathway. Its activated form, ixa, forms a complex with factor viii and calcium on platelet factor 3 to activate factor x to xa. Deficiency of factor ix results in christmas disease (haemophilia b). Chemical name: Blood-coagulation factor IX (12 Dec 1998) |
| habitat component | <ecology> A single element (for example, velocity, depth, cover, etc.) of the habitat or environment in which a fish or other aquatic species or population may live or occur. (09 Oct 1997) |
| secretory component | <physiology> A glycoprotein found in a variety of external secretions (tears, bile, colostrum) usually complexed to secreted polymeric immunoglobulins (IgA or, less frequently IgM). It is derived, by proteolytic cleavage, from the polymeric immunoglobulin receptor (receptors, polymeric immunoglobulin) and probably functions to protect the immunoglobulins from proteolysis in the secretions. (12 Dec 1998) |
| secretory component of IgA | <immunology, protein> A polypeptide chain of about 60 kD that aids secretion of the IgA, a portion of the IgA receptor on the plasmalemma of the inner side of the epithelial cells lining the gut, which is proteolysed when the IgA receptor complex has travelled through the cell after receptor mediated endocytosis at the inner face, to the outer (luminal) face. (18 Nov 1997) |
| serum amyloid P component | Precursor of amyloid component P, found in basement membrane. Member of the pentraxin family. See: serum amyloid. (18 Nov 1997) |
| two-component plasma | <radiobiology> Refers to a plasma containing a cool thermal component and a population of high energy particles (such as from neutral beam injection) which are in the process of thermalising (slowing down). (09 Oct 1997) |
| fast component | <molecular biology> A segment of eukaryotic DNA consisting of highly-repeated nucleotide sequences which, when the entire duplex DNA molecule is denatured (the double-stranded helix comes apart and becomes single strands) and then allowed to renature (the complementary single strands come together to form a helix), will be the first segment to renature. (09 Oct 1997) |