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 ?
Additional Gene Segments: Each of the variable regions is actually a combination of multiple gene segments; for the light chain, V+J; for the heavy chain, V+D+J;
SSCP analysis of the horse mtDNA D-Loop variable region fragments was performed on gels of 10% w/v acrylamide:bis-acrylamide (49:1), 0.
Using the 180-bp ompA gene variable region we sequenced in this study, we differentiated R.
Use of family specific leader region primers for PCR amplification of the human heavy chain variable region gene repertoire.
MLST is complemented by antigen sequence typing of the variable regions of the outer membrane proteins PorA and FetA (9).
Fab, the variable region of an immunoglobulin, containing the antigen combining site and idiotope.
The XOMA Human Engineering(TM) (HE(TM)) technology is a novel method to reduce the immunogenicity of an antibody variable region, and an attractive alternative to CDR-grafting methods of antibody humanization.
The additional genome regions that have been described thus far include the E183L and CP204L gene regions, encoding the p54 and p30 proteins, respectively, as well as the central variable region within the open reading frame (ORF) B602L.
The two patents listed above specifically contain claims covering genetically modified mice that have unrearranged human immunoglobulin variable region gene segments at endogenous mouse immunoglobulin loci.
We combined MLST data with sequence data of the short variable region (SVR) of the flaA and flaB loci, previously used to type Campylobacter spp.
Unlike methods based on CDR grafting, the XOMA human engineering method analysed each amino acid position in the antibody variable region.
DART therapeutics can accommodate virtually any variable region sequence in a "plug-and-play" fashion, are highly potent, and have very favorable manufacturing properties.

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