Genetic factors and polypeptide chain subclasses of human immunoglobulin G detected in chimpanzee serums

The Gm and Inv genetic factors, characteristic antigens of human immunoglobulin G, were detected in chimpanzee serums. All animals tested were Gm(a+, x-, b(l)-, b(2)-, b(3)+, b(4)+). Polymorphism was demonstrated for factors Gm(c), Inv(l), and Inv(b). Three of the subclasses of heavy polypeptide chains and both types of light polypeptide chains that are present in human immunoglobulin G were identified in chimpanzee serums.     

Variation and homology in the mu and gamma heavy chains of human immunoglobulins

Sequence analysis of an 1gM immunoglobulin shows that the variable regions of hunman micro and gamma1 heavy chainis may have twice as much homology as their constant regions and that evolutionary divergence of micro and gamma1 heavy chain genes occurred not long after the separation of heavy and light chain genes.     

Plasma 3S gamma-1-globulin: identity with erythrocyte carbonic anhydrase B

The 3S (gamma1), 2S (gamma2), and 0.5S (gamma2) fractions of human plasma are heterogeneous in protein composition. Although each fraction contained a relatively small amount of protein antigenically related to the immunoglobulin light chains, most of the proteins were unrelated to immunogloublin G or its light chains. Of the 3S (gamma1)-globulins the greater part was immunochemically identical to carbonic anhydrase B and had carbonic anhydrase activity. These findings explain earlier reports of an immunochemical similarity between 3S (gamma1)-globulins and immunoglobulin light chains in spite of marked differences in amino acid and peptide composition between the two. Apparently not all plasma gamma-globulins are necessarily immunoglobulins.     

Antibody active sites and immunoglobulin molecules

In order to obtain detailed information about the relationship between structure and function in antibody molecules, a method called affinity labeling has been devised to attach chemical labels specifically to amino acid residues in the active sites of antibody molecules. With antibodies to three different haptens, highly specific labeling of the active sites has been achieved. Tyrosine residues on both heavy and light polypeptide chains have been labeled in a molar ratio close to 2:1, and labels on the two chains are equally specific to the active sites. Peptide fragmentation studies of the labeled chains of one antibody system have shown that: (i) within 25 amino acid residues of the labeled tyrosine on either chain, substantial chemical heterogeneity exists among different antibody molecules of the same specificity; and (ii) the labeled peptide fragments from both chains are very similar in physicochemical characteristics, including average size, heterogeneity, and unusual hydrophobicity. These experimental results have led us to the view that a particular region of the heavy chain and a particular region of the light chain are utilized to construct the active sites of the three different antibodies, differences in specificity arising from chemical perturbations in these two regions. Correlated structural studies of affinity-labeled antibodies and of the homogeneous light chains (Bence Jones proteins) and heavy chains produced in multiple myeloma may permit the identification of these special active-site regions. The view that active sites of different specificity are chemical perturbations of a particular region of the antibody molecule has a possible close analogue in enzyme systems, particularly among the esterases. The marked chemical similarities we have observed between the active site regions of heavy and light chains indicate to us that chemical homologies, but not identities, exist between the chains. This is reinforced by recently obtained amino acid sequence data which reveal homologies between the two chains near their carboxyl-terminals. These results indicate that the structural genes which code for the synthesis of heavy and light chains are related, presumably having arisen from some common ancestral gene during evolution. This conclusion strongly suggests that both heavy and light chains determine antibody specificity, and has important implications for the still-unknow mechanisms of antibody biosynthesis.     

Chromosomal locations of the murine T-cell receptor alpha-chain gene and the T-cell gamma gene

Two independent methods were used to identify the mouse chromosomes on which are located two families of immunoglobulin (Ig)-like genes that are rearranged and expressed in T lymphocytes. The genes coding for the alpha subunit of T-cell receptors are on chromosome 14 and the gamma genes, whose function is yet to be determined, are on chromosome 13. Since genes for the T-cell receptor beta chain were previously shown to be on mouse chromosome 6, all three of the Ig-like multigene families expressed and rearranged in T cells are located on different chromosomes, just as are the B-cell multigene families for the Ig heavy chain, and the Ig kappa and lambda light chains. The findings do not support earlier contentions that genes for T-cell receptors are linked to the Ig heavy chain locus (mouse chromosome 12) or to the major histocompatibility complex (mouse chromosome 17).     

Immunoglobulin production: method for quantitatively detecting variant myeloma cells

Mouse myeloma cells in continuous culture were cloned in soft agar. The clones were assayed for their ability to synthesize heavy and light chains of gamma globulin by immunoprecipitation directly in the agar. A minor population secreting only light chains was identified. The two cell types were recloned and a low incidence of conversion of 7S to light-chain production was demonstrated. This technique can be used to isolate rare variants of cells secreting specific macromolecules.     

犬血清IgG的纯化、抗体制备及其鉴定

[目的]探讨犬血清IgG的纯化方法。[方法]采用硫酸铵盐析法结合SephadexG-200凝胶柱层析提取纯化犬血清IgG,利用SDS-PAGE电泳和免疫印迹法鉴定所得产品的纯度和免疫活性。[结果]获得的纯化犬血清IgG的SDS-PAGE图谱中存在2条蛋白条带,表明获得了高纯度的犬血清IgG;重链分子量为58kD,轻链分子量为27kD,IgG分子量为170kD。特异性检测发现犬血清IgG重链和轻链都能与鼠抗犬血清IgG抗体结合,表明纯化犬血清IgG具有免疫原性和反应原性。[结论]硫酸铵盐析法结合SephadexG-200凝胶柱层析可获得纯度高、活性好的纯化犬血清IgG,为犬血清IgG相关的免疫学试验提供了高质量的免疫材料。     

Macroglobulin structure: variable sequence of light and heavy chains

The variable regions of the light and heavy chains on the same macroglobulin (immunoglobulin M) molecule are no more related in amino acid sequence than are the variable regions of the light and heavy chains of different immunoglobulin molecules. Subgroups of micro chains are similar in their variable sequence to subgroups of gamma chains.     

Complete amino acid sequence of the Mu heavy chain of a human IgM immunoglobulin

The amino acid sequence of the micro, chain of a human IgM immunoglobulin, including the location of all disulfide bridges and oligosaccharides, has been determined. The homology of the constant regions of immunoglobulin micro, gamma, alpha, and epsilon heavy chains reveals evolutionary relationships and suggests that two genes code for each heavy chain.     

Immunoglobulin structure: amino terminal sequences of mouse myeloma proteins that bind phosphorylcholine

The amino terminal sequences of five light and heavy immunoglobulin chains from myeloma proteins of the BALB/c mouse with binding activity to phosphorylcholine are presented. Except for a single substitution in position 4, all five heavy chains have identical amino terminal sequences through the first hypervariable region. Proteins which share unique (idiotypic) antigenic determinants are identical through the first hypervariable region of their light and heavy chains. Proteins with differing idiotypic determinants have light chains of differing amino acid sequence. These observations suggest that the heavy chain plays a more important role than the light chain in determining the phosphorylcholine binding site.     

Light chains of rabbit immunoglobulin: assignment to the kappa class

Normal rabbit gamma globulin was reduced under conditions presumed to break only interchain disulfide bridges, and the reduiced product was then blocked with C(14)-iodoacetamide. The light chains were separated from the heavy chains and subjected to peptic digestion. Two radioactive peptides were recovered from the digest. The peptides are apparently overlapping and represent the carboxyterminuis. Comparison of this region in the rabbit light chains with the corresponding amino acid sequences in various mouse and human light chains indicates that the rabbit light chains are of the (K)-class.     

2 types of lambda polypeptide chains in human immunoglobulins

Two antigenic subtypes of human lambda polypeptide chains were distinguished by rabbit antiserum produced to a lambda Bence Jones protein. Lambda Bence Jones proteins and G myeloma proteins with lambda light chains were identified as being in one or the other subtype. The Oz (+) lambda chain subtype is present in light chains from pooled normal human immunoglobulin G and in whole normal immunoglobulin G molecules.     

A test of clathrin function in protein secretion and cell growth

Clathrin-coated membranes are intimately associated with a variety of protein transport processes in eukaryotic cells, yet no direct test of clathrin function has been possible. The data presented demonstrate that Saccharomyces cerevisiae does not require clathrin for either cell growth or protein secretion. Antiserum to the yeast clathrin heavy chain has been used to isolate a molecular clone of the heavy chain gene (CHC1) from a library of yeast DNA in lambda gt11. Clathrin-deficient mutant yeast have been obtained by replacing the single chromosomal CHC1 gene with a disrupted version of the cloned DNA. Cells harboring a nonfunctional chc1 allele produce no immunoreactive heavy chain polypeptide, and vesicles prepared from mutant cells are devoid of clathrin heavy and light chains. Although clathrin-deficient cells grow two to three times more slowly than normal, secretion of invertase occurs at a nearly normal rate. Therefore protein transport through the secretory pathway is not obligately coupled to the formation of clathrin-coated vesicles.     

Inhibition of self-binding antibodies (autobodies) by a VH-derived peptide

The self-binding properties of a dominant idiotypic antibody (T15) and a minor idiotypic antibody (M603), both specific for phosphorylcholine, were examined as models of self-binding antibodies (autobodies). Observed differences in the self-binding affinity of T15 and M603 relate to variable sequence differences in their respective heavy and light chains. A molecular recognition theory based on the translation of coding and noncoding DNA strands was used to identify complementary amino acid sequences responsible for self-binding. The second hypervariable region of the heavy chain domain, extending into the third framework region, was predicted as the primary self-binding locus. Among peptides synthesized with different variable heavy and light chain regions, a 24-residue peptide spanning the second hypervariable and third framework regions of the heavy chain of T15 was nearly as effective as phosphorycholine in inhibiting the self-binding complexes.     

Alpha-chain disease: a new immunoglobulin abnormality

A new type of pathological immunoglobulin was found in the serum, urine, and saliva of a young Arab patient with abdominal lymphoma and diffuse lymphoplasmacytic infiltration of the small intestine. This protein is devoid of light chains and is closely related to the alpha polypeptide chains of the gamma(A1) (Le) subclass of immunoglobulin A. It is characterized by electrophoretic heterogeneity, tendency toward polymerization, and a high carbohydrate content. No intracellular synthesis of light chain was detected.     

Clathrin light chains LCA and LCB are similar, polymorphic, and share repeated heptad motifs

The clathrin light chains fall into two major classes, LCA and LCB. In an intact clathrin triskelion, one light chain, of either class, is bound to the proximal segment of a heavy chain leg. Analysis of rat brain and liver complementary DNA clones for LCA and LCB shows that the two light chain classes are closely related. There appear to be several members of each class having deletions of varying length aligned at the same position. A set of ten heptad elements, characteristic of alpha-helical coiled coils, is a striking feature of the central part of each derived amino acid sequence. These observations suggest a model in which the alpha-helical segment mediates binding to clathrin heavy chains and the amino- and carboxyl-terminal segments mediate interactions with other proteins. They also suggest an explanation for the observed tissue-dependent size variation for members of each class.     

Hemoglobin Portland 1: a new human hemoglobin unique in structure

A new hemoglobin (Hb), Portland 1, has been found in a newborn infant having multiple congenital anomalies and complex autosomal chromosomal mosaicism. The new hemoglobin has a unique tetrameric structure (molecular weight, 66,000) composed of two pairs of different types of chains, neither of which is alpha, gamma(2)x(2). The x-chain of Hb Portland 1 may be a new type of hemoglobin chain, but the available evidence suggests that it may be identical with the epsilon chain. We suggest that Hb Portland 1 is an embryonic hemoglobin that persisted until after birth in relatively large amounts in this patient.     

Focused evolution of HIV-1 neutralizing antibodies revealed by structures and deep sequencing

Antibody VRC01 is a human immunoglobulin that neutralizes about 90% of HIV-1 isolates. To understand how such broadly neutralizing antibodies develop, we used x-ray crystallography and 454 pyrosequencing to characterize additional VRC01-like antibodies from HIV-1-infected individuals. Crystal structures revealed a convergent mode of binding for diverse antibodies to the same CD4-binding-site epitope. A functional genomics analysis of expressed heavy and light chains revealed common pathways of antibody-heavy chain maturation, confined to the IGHV1-2*02 lineage, involving dozens of somatic changes, and capable of pairing with different light chains. Broadly neutralizing HIV-1 immunity associated with VRC01-like antibodies thus involves the evolution of antibodies to a highly affinity-matured state required to recognize an invariant viral structure, with lineages defined from thousands of sequences providing a genetic roadmap of their development.