variable region


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im·mu·no·glob·u·lin (Ig),

(im'yū-nō-glob'yū-lin),
One of a class of structurally related proteins, each consisting of two pairs of polypeptide chains, one pair of light (L) low molecular weight chains (κ or λ), and one pair of heavy (H) chains (γ, α, μ, δ, and ε), usually all four linked by disulfide bonds. On the basis of the structural and antigenic properties of the H chains, immunoglobulins are classified (in order of relative amounts present in normal human serum) as IgG (7S in size, 80%), IgA (10-15%), IgM (19S, a pentamer of the basic unit, 5-10%), IgD (less than 0.1%), and IgE (less than 0.01%). All of these classes are homogeneous and susceptible to amino acid sequence analysis. Each class of H chain can associate with either κ or λ L chains. Subclasses of immunoglobulin, based on differences in the H chains, are referred to as IgG1, etc.
When split by papain, IgG yields three pieces: the Fc piece, consisting of the C-terminal portion of the H chains, with no antibody activity but capable of fixing complement, and crystallizable; and two identical Fab pieces, carrying the antigen-binding sites and each consisting of an L chain bound to the remainder of an H chain.
Antibodies are immunoglobulins, and all immunoglobulins probably function as antibodies. However, immunoglobulin refers not only to the usual antibodies, but also to a great number of pathologic proteins classified as myeloma proteins, which appear in multiple myeloma along with Bence Jones proteins, myeloma globulins, and immunoglobulin fragments.
From the amino acid sequences of Bence Jones proteins, it is known that all L chains are divided into a region of variable sequence (VL) and one of constant sequence (CL), each comprising about half the length of the L chain. The constant regions of all human L chains of the same type (κ or λ) are identical except for a single amino acid substitution, under genetic controls. H chains are similarly divided, although the VH region, although similar in length to the VL region, is only one third or one fourth the length of the CH region. Binding sites are a combination of VL and VH protein regions. The large number of possible combinations of L and H chains make up the "libraries" of antibodies of each individual.

variable region

n.
The portion of the amino terminal of an immunoglobulin's heavy and light chains having a variable amino acid sequence.

variable region

the part of an immunoglobulin in which the amino acid sequence can differ among molecules of that class of immunoglobulin. The variable region includes the antigen-binding site. Compare constant region.

variable region

The part of an antibody at the tip of each arm (N-terminal region) that varies considerably in its amino acid sequence from one antibody to another. The remaining parts of the structure of antibodies are fixed and almost identical. This region is coded for by the V gene.

variable (V) region

an area of an IMMUNOGLOBIN molecule that is specific to that particular molecule. Compare CONSTANT REGION.

variable region

the N-terminal portion of heavy and light chains of immunoglobulin molecules in which the amino acid sequence varies as a consequence of somatic mutation and recombination during ontogeny of B lymphocytes and also occurring after antigen exposure. The variable amino acid sequence which provides more than 107 different antibody molecules is responsible for the antigen-binding specificity.
References in periodicals archive ?
pylori isolated from the region posses with cagA-positive strains and cagA 3' variable region of most H.
Analysis of the immunoglohulin heavy chain variable region gene expression in Iranian patients with chronic lymphocytic leukemia.
Ogata, "Preferential Expression of Variable Region Heavy Chain Gene Segments by Predominant 2,4-Dinitrophenyl-Specific Balb/C Neonatal Antibody Clonotypes," Proceedings of the National Academy of Science USA 83, no.
Primers used to amplify a 444 bp fragment of the horse mtDNA D-loop variable region were generated from horse mtDNA published sequence (Ishida et al.
Next-Generation Sequencing of Immunoglobulin Heavy Chain Variable Region in Diagnostic Samples of Pediatric Acute Lymphoblastic Leukemia Identifies Hundreds of Clonal Subpopulations with Multiple Immunophenotypes (Abstract 1436)
A follow-up study is under way in the region to genetically characterize the viruses in this outbreak, focusing on the p54, p30 and, central variable region genes.
Diabody: In a scFv expression vector, the cDNAs that encode the heavy-chain variable region (VH) and the light-chain variable region (VL) of an antibody are assembled via the sequence encoding a linker peptide.
The Human Engineering technology enables the derivation of humanized variable region amino acid sequences from mature mouse variable region amino acid sequences.
meningitidis were further tested in a nestedporA PCR, followed by sequencing the porA gene to identify the 2 variable region peptide loops of the PorA protein (5).
The molecular characterization of the most variable region of the mitochondrial cytochrome oxidase I gene and of the ribosomal 28S gene has been performed for the third-stage larvae collected from cattle and yaks in China and identified (on the basis of the spinulation on the ventral side of the 10th segment) as H.
In ribotyping hyper variable region V4 of 18S rRNA gene was amplified in five isolates which were found to be genomically diverse in RAPD analysis.

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