| CAAX [box] | protein segment in which C is cysteine, A is usually but not always an aliphatic amino acid, and X i... |
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| EAAC | excitatory amino acid carrier |
| GABOA | gamma-amino-beta-hydroxybutyric acid |
| GOBAB | gamma-hydroxy-beta-amino-butyric acid |
| LAAO | L-amino acid oxidase |
| myosin light chain | <protein> The light chains of the muscle protein myosin. Each molecule of myosin is composed of two heavy chains and two pairs of light chains. The light chains have a molecular weight of about 20 kD and there is one dissimilar pair of light chains associated with each heavy chain. The proteins all have sequence homology to calmodulin, but not all with calcium binding activity. Several types are known: regulatory light chains (LC 2, DNTB light chains) probably regulate the ATPase activity of the heavy chain directly (through the binding of calcium) or indirectly (activating when they themselves are phosphorylated by myosin light chain kinase) and essential light chains (LC 1, LC 3, alkali light chains), which have a more subtle and apparently nonessential role. In molluscan muscle the EDTA light chains (similar to LC 2 from vertebrate muscle) confer calcium sensitivity on the myosin itself. The light chains are "calmodulin-like" proteins that bind calcium. Two of them can be removed easily, and two with difficulty. The light chains bind the heavy chains in the vicinity of the head groups of the myosin. (12 Dec 1998) |
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| myosin light chain kinase | <enzyme> An enzyme that phosphorylates myosin light chains in the presence of ATP to yield myosin-light chain phosphate and ADP, and requires calcium and calmodulin. The 20-kD light chain is phosphorylated more rapidly than any other acceptor, but light chains from other myosins and myosin itself can act as acceptors. The enzyme plays a central role in the regulation of smooth muscle contraction. Chemical name: ATP:myosin-light-chain O-phosphotransferase Registry number: EC 2.7.1.117 (12 Dec 1998) |
| haemolytic chain | The haemolysis that occurs when complement is activated by the previously formed union of erythrocytes and specific antibody. (05 Mar 2000) |
| H chain | <protein> Heavy chain of immunoglobulin, see IgG, IgM, etc. (18 Nov 1997) |
| heavy chain | <protein> In general, the larger polypeptide in a multimeric protein. Thus the immunoglobulin heavy chain is of 50 kD, the light chain of 22 kD, whereas in myosin the heavy chain is very much larger (220 kD) than the light chains (~20 kD). (18 Nov 1997) |
| heavy chain disease | A disorder of immunoglobulin synthesis in which large quantities of abnormal heavy chains are excreted in the urine. The amino acid sequences of the n- (amino-) terminal regions of these chains are normal, but they have a deletion extending from part of the variable domain through the first domain of the constant region, so that they cannot form cross-links to the light chains. The defect arises through faulty coupling of the variable (v) and constant (c) region genes. (12 Dec 1998) |
| short chain | In bacteriology, a string of two to eight cells. (05 Mar 2000) |
| short-chain acyl-CoA dehydrogenase | See: acyl-CoA dehydrogenase (NADPH+). (05 Mar 2000) |
| short-chain beta-hydroxyacyl-CoA dehydrase | <enzyme> Forms trans-2-enoyl-CoA; maximal activity with trans-2-hexenoyl-CoA, followed by crotonyl-CoA; not the same as EC 4.2.1.17 Registry number: EC 4.2.1.- Synonym: beta-hydroxybutyryl-CoA dehydrase, short-chain beta-hydroxyacyl-coenzyme a dehydrase (26 Jun 1999) |
| nuclear chain fibre | The shortest and most numerous type of intrafusal muscle fibre's in a neuromuscular spindle, containing a single row of centrally positioned nuclei. (05 Mar 2000) |
| delta chain | See: immunoglobulin. The heavy chains of mouse and human IgD immunoglobulins. (18 Nov 1997) |
| immunoglobulins, alpha-chain | Heavy chains found in the fab and fc fragments of IgA and having a molecular weight of approximately 58 kD. They contain about 470 amino acid residues arranged in four domains and an oligosaccharide component bound covalently to the fc fragment. (12 Dec 1998) |
| immunoglobulins, delta-chain | Heavy chains found in the fab and fc fragments of IgD and having a molecular weight of approximately 64 kD. They contain about 500 amino acid residues arranged in four domains and an oligosaccharide component covalently bound to the fc fragment. (12 Dec 1998) |
| immunoglobulins, epsilon-chain | Heavy chains found in the fab and fc fragments of IgE and having a molecular weight of approximately 72 kD. They contain about 550 amino acid residues arranged in five domains and about three times more carbohydrate than the heavy chains of IgA, IgD, and IgG. (12 Dec 1998) |
| immunoglobulins, gamma-chain | Heavy chains found in the fab and fc fragments of IgG and having a molecular weight of approximately 51 kD. They contain about 450 amino acid residues arranged in four domains and an oligosaccharide component covalently bound to the fc fragment. The gamma chains of the four IgG subgroups are not identical, but resemble each other more closely than the heavy chains of a different immunoglobulin. (12 Dec 1998) |