Sequence studies of the Fd section of the heavy chain of rabbit immunoglobulin G

Rabbit immunoglobulin allotypes: structure, immunology, and genetics

Over a 6-month period, 157 patients, 89 of whom had central nervous system tumors, were examined on a prototype 0.12 T resistive nuclear magnetic resonance (NMR) imaging unit. All of the patients had computed tomography (CT), which was used as a standard to which the NMR findings were compared. Studies were done primarily by saturation-recovery technique with short repetition times. The signal intensity with saturation-recovery technique did not allow differentiation among most tumor types. Location, extent, and morphology helped to some extent in attempts at differentiation. In the multiplanar mode, NMR compared favorably to CT with regard to lesion detection. Limited early experience suggests that NMR also may detect some lesions when the CT is negative and may detect additional lesions when one or more are present. The NMR examination was well tolerated by selected patients.

Nucleotide sequence of a rabbit IgG heavy chain from the recombinant F-I haplotype

We report the sequence of a cDNA encoding a rabbit immunoglobulin gamma heavy chain of d12 and e14 allotypes with high homology to partial cDNA sequences from rabbits of d11 and e15 allotypes. The encoded rabbit protein shows homologies with human (68-70%) and mouse (60-63%) gamma chains. The nucleotide sequence homologies of the CH domains range from 76-84% with human and 64-76% with mouse sequences. Comparison of the portion of VH encoding amino acid positions 34-112 with a previously determined VH sequence of the same allotype shows high conservation of sequences in the second and third framework segments but more marked differences both in length and encoded amino acids of the second and third complementarity-determining regions (CDRs). We also found a high degree of homology with a human genomic V-region, VH26 (77%) and a remarkable similarity between rabbit and human second CDR sequences and human genomic D minigenes. These results provide additional evidence that D minigene sequences share information with the CDR2 portion of VH regions.

A thermodynamic study of cooperative structures in rabbit immunoglobulin G

The intramolecular melting of rabbit immunoglobulin G and its proteolytic fragments has been studied by scanning microcalorimetry in the acidic pH region. By thermodynamic analysis of the heat capacity function the following conclusions have been made. 1. The Fab and Fc fragments in IgG molecules are thermodynamically practically independent subunits in the pH region studied. 2. The Fab fragment exhibits three cooperative transitions at melting. Two of these transitions are explained assuming that equivalent domains in this fragment are paired, forming two cooperative blocks, while the third transition seems to correspond to the disruption of contacts between these cooperative blocks. 3. Fc and pFc' fragments exhibit four and two cooperative transitions, respectively. These transitions can be explained only by assuming that each of the structural domains of these fragments consists of two subparts and that the pairs of equivalent subparts are merged into the cooperative blocks thus forming four cooperative blocks in the Fc fragment.

Molecular cloning of rabbit gamma heavy chain mRNA

A cDNA library of rabbit spleen mRNA was screened for immunoglobulin heavy chain sequences. In this paper we report the nucleotide sequence of two cDNA clones containing part of the constant region of the rabbit gamma heavy chain mRNA. The sequence encodes part of the CH2 domain (amino acids 268 to 340), the entire CH3 domain (amino acids 341 to 447) and the 3' untranslated region. This nucleotide sequence has been compared to the corresponding sequences of mouse gamma 1, gamma 2a and gamma 2b genes. The homologies between rabbit gamma chain gene sequence and each of the mouse gamma chain gene sequences are of the same magnitude order. This comparison shows that the CH2 domains are more homologous to each other than CH3 domains or 3' untranslated sequences. The presence of species specific nucleotide positions suggests that mouse gamma chain genes could have evolved from a common ancestor shortly after the mouse-rabbit species separation. Genomic blot analysis of rabbit liver DNA with the rabbit C gamma probes shows a limited number of related sequences, with little restriction site polymorphism between individual rabbits.

Proximity relationships within the Fc segment of rabbit immunoglobulin G analyzed by resonance energy transfer

Resonance energy transfer analysis has been carried out with a noncovalent rabbit hybrid of immunoglobulin G (IgG) composed of normal rabbit IgG and rabbit anti-lactose IgG. The hybrid IgG was prepared from proteins in which the single inter-heavy-chain disulfide linkage was specifically reduced and alkylated. Normal rabbit IgG was alkylated with the iodoacetyl derivative of N-(aminoethyl)-5-naphthylamine-1-sulfonic acid while the rabbit anti-lactose IgG was alkylated with either iodoacetamide or the iodoacetyl derivative of p-[[p-(dimethylamino)phenyl]azo]aniline. Fractionation with an anti-lactose-specific immunoadsorbent yielded a population in which each fluorescent donor [N-[(acetylamino)ethyl]-5-naphthylamine-1-sulfonic acid] was adjacent to a nonfluorescent acceptor [N-acetyl-p[[p-dimethylamino)phenyl]. Data on fluorescence quantum yield, excited-state lifetime, time-resolved emission anisotropy, and steady-state fluorescence polarization revealed a distribution of distances between the donor and acceptor. In the native molecule, the hinge regions are known to be covalently liked by a single disulfide bond. In the absence of this linkage, the hinge regions were separated such that for a majority of the molecules in solution (approximately 60%) the separation was 50-60 A. In the context of current knowledge of the IgG molecule, it is evident that the principle forces maintaining the integrity of the native, functional Fc segment are the strong noncovalent interactions of the CH3 domains and the single inter-heavy-chain disulfide bond.

Isolation of an active heavy-chain variable domain from a homogeneous rabbit antibody by cathepsin B digestion of the aminoethylated heavy chain

Cathepsin B from bovine liver has been used to cleave the heavy chain of partially reduced and aminoethylated rabbit allotype a1 IgG. Three major cleavages have been identified, one of which appears to be at the peptide bond carboxy terminal to the two adjacent (aminoethyl)cysteine residues at positions 133 and 134. The variable domain of the heavy chain (VH) was isolated by gel filtration from both pooled heterogeneous rabbit IgG and a homogenous rabbit antitype III pneumococcal polysaccharide antibody. This VH inhibited the binding of 125I-labeled (allotype a) IgG to anti-a1 allotypic antibodies. The recombinant molecule consisting of VH and light chain from the homogeneous antibody is active in an antigen binding assay.

J segment in human delta chains

We report the complete sequence of a cyanogen bromide fragment of a human delta chain (ErI). Its interest lies in the fact that it contains the peptide joining the V delta to the C delta 1 region. The presented sequence is compared with the homologous region of other human heavy chain classes and subclasses. The possibility that human delta chains and other human heavy chains have in their chromosomal DNA a short J sequence, is discussed.

Cloning immunoglobulin gamma 2b chain gene of mouse: characterization and partial sequence determination

DNA from newborn mice was digested with restriction endonuclease EcoRI, and a 6.6-kilobase fragment encoding immunoglobulin gamma 2b chain mRNA derived from MPC 11 myeloma was enriched about 100-fold by RPC-5 column chromatography and agarose gell electrophoresis. The 6.6-kilobase fragment was cloned with lambda gt WES.lambda B as EK2 vector. The cloned phage (lambda WES.IgH22) contained the constant region gene of the gamma 2b chain but not the variable region gene of MPC 11 mRNA. The constant region genes of the other gamma chains (i.e., gamma 1, gamma 2a, and gamma 3) were not present in lambda gt WES.IgH22 DNA. R-loop mapping indicates that the gamma 2b chain structural gene is divided into two parts (330 +/- 60 SD base pairs and 930 +/- 110 SD base pairs) by an intervening sequence (360 +/- 100 SD base pairs). The nucleotide sequence around the junction of the hinge region and CH2 domain was determined and shown to match the amino acid sequence of the initial part of the CH2 domain of the gamma 2b chain. The base sequence upstream from the junction, however, is unrelated to the amino acid sequence of the CH1 domain and the hinge region of all the gamma chains whose sequences have been determined. These results indicate that the gamma 2b chain gene is interrupted at the junction of the hinge region and CH2 domain by an intervening sequence. The existence of two more intervening sequences, one between the CH1 domain and the hinge region and the other between the CH2 and CH3 domains, is discussed.

The binding of rabbit IgG and its enzymatically derived fragments to homologous peritoneal macrophages

Rabbit IgG and its Fab, Fc and pFc' fragments, prepared by papain or peptic digestion, were assayed for binding to homologous peritoneal macrophages. The binding affinity of IgG for the peritoneal macrophages (Ka = 5.9 +/- 1.6 x 10(5) L/M) was comparable to that recorded with alveolar macrophages (7.6 +/- 1.8 x 10(5) L/M, Arend & Mannik, 1973) but the number of receptor sites per peritoneal cell (4.6 +/- 2.1 x10(6)) was about four-fold greater than on the latter. Of the fragments, only Fc bound to macrophages with an affinity comparable to intact IgG; pFc' bound weakly and Fab was totally inactive. These data, taken with a recent study involving rabbit IgG and guinea-pig macrophages (Ovary, Saluk, Quijada & Lamm, 1976), indicate that the primary IgG binding site for macrophages is located in the C gamma 2 domain.

Homogeneous rabbit immunoglobulin lacking group a allotypes: amino acid sequence analysis of the heavy chain

The partial amino acid sequence of rabbit a-negative heavy chain has been determined for residues 1--43 as: less than EEQLEESGGGLVQPGGSLKLSCKGSGFDFSVYGVTWVRQAPGK; and for residues 64--120 as: MNGRFTISSDNAQNRLYLQLNSLTAADTATYFCARSMVVVAGVHSYFDVWGPGTLVTV. Comparison of this sequence with the human heavy chain subgroup III shows homology of 78% suggesting that a common ancestral variable region gene existed in mammals prior to speciation. The constant region of the a-negative chain is structurally identical with that of a-positive chains, whereas the variable region differs substantially between a-positive and a-negative molecules. These findings support the concept that two genes encode one immunoglobulin polypeptide chain and demonstrate the existence in the rabbit of variable region subgroups similar to those reported for humans and other species. A novel approach to the initial fragmentation of the heavy chain was developed in this study. This method, which involved digestion of the H chain with the protease V8, produced a free N terminus and should have wide application in future studies on heavy chains with blocked amino terminals.

Determination of the primary structure of a mouse IgG2a immunoglobulin. Amino-acid sequence of the H4 cyanogen-bromide fragment

The complete amino acid sequence of CNBr fragment H4 of the murine immunoglobulin MOPC 173 (IgG2a,chi) has been determined, thus completing the sequence determination of the entire heavy chain. The H4 fragment contains 150 residues, and extends from residue 105 to residue 254 of the heavy chain, which appears thus to be composed of 447 amino acids residues. This fragment contains the end of the V region, the switch peptide, the CH1 domain, the hinge region and the beginning of CH2. Sequence comparisons suggest that the CH1 domain is highly conserved in evolution, and allows the definition of two additional isotypic-specific regions.

Sequence studies on the constant region of the Fd sections of rabbit immunoglobulin G of different allotype

The amino acid sequence has been completed for the constant region of the Fd fragments of heavy chains from rabbit IgG (immunoglobulin G) of allotype Aa1 and Aa3. The amino acid sequence given by Fruchter et al. [(1970) Biochem. J. 116, 249-259] for the constant region of the Fd fragment from Aa1 IgG was extended and in in part corrected to give a continuous sequence of 140 residues. No allotype-related sequence variation was found in the constant section of the Fd fragment. This evidence confirms the view that the differences in sequence between the variable regions of Aa1 and Aa3 IgG [Mole et al., (1971) Biochem. J. 124, 301-318] are responsible for the allotypic specificities.

Fixation of the first component of complement by immune complexes: effect of reduction and fragmentation of antibody

The integrity of both covalent and non-covalent bonds between the heavy chains of rabbit immunoglobulin gamma antibody is essential for maximal efficiency of binding of the first component of complement to immune complexes.

Comparison of the amino acid sequences of the variable domains of two homogeneous rabbit antibodies to type III pneumococcal polysaccharide

The amino acid sequences of the V (variable) regions of the H (heavy) and L (light) chains derived from rabbit antibody K-25, specific for type III pneumococci, were determined; this is the second homogeneous rabbit antibody besides antibody BS-5 whose complete sequence of the V domain has been established (Jaton, 1974d). The V regions of L chains BS-5 and K-25 (both of allotype b4) differ from each other by 19 amino acid residues; 11 of these 19 substitutions are located within the three hypervariable sections of the V region. On the basis of seven amino acid differences within the N-terminal 28 positions, it is suggested that L chain K-25 belongs to a different subgroup of rabbit K chains and L chain BS-5. H chain K-25 (allotype a2) differs from another H chain of the same allotype by one amino acid substitution within the N-terminal 70 positions in addition to interchanges occurring in the first two hypervariable sections. H chain K-25 was compared with H chain BS-5 (allotype a1) and with the known V-region rabbit sequences. Allotype-related differences between a1, a2 and a3 chains appear to occur within the N-terminal 16 positions and possibly in scattered positions throughout the V-region. In the hypervariable positions, variability between the two antibodies is remarkably more pronounced within the third hypervariable section of both H and L chains than within the first two.

Partial amino acid sequence of rabbit beta2-microglobulin

The amino acid sequence of the first 35 residues of a low-molecular-weight protein obtained from the urine of rabbits treated with sodium dichromate was determined and shown to be identical with human beta2-microglobulin in 30 positions. Rabbit beta2-microglobulin, like the human protein, is strikingly homologous to the constant regions of rabbit immunoglobulin G, particularly the CH3 region.

Completion of the analysis of the primary structure of the variable domain of a homogeneous rabbit antibody to type III pneumococcal polysaccharide

The amino acid sequence between residues 70 and 116 of the V (variable) region of the H (heavy) chain derived from rabbit antibody BS-5, specific for type III pneumococcal polysaccharide, was determined. The sequence of this section of the H chain which includes the hypervariable residues 94 to about 112 was unique, although minor variant sequences present in the H chain preparation would not have been detected by the techniques used in this work. Taken together with the known sequences of the N-terminal 69 residues of H chain BS-5 (Jaton & Braun, 1972) and of the V region of the light chain (Jaton, 1974b), the data establish the complete sequence of the V domain of a rabbit immunoglobulin G. The V region of H chain BS-5 is compared with the basic sequences of the three human V region subgroups known to date, with one mouse H chain, and with guinea-pig pooled H chains. Even though chains from guinea pig and mouse clearly belong to the subgroup III of variability (V(HIII)), rabbit H chain BS-5 (allotypic variant a(1)) appears more closely related to the subgroup V(HII) than to the subgroups V(HIII) or V(HI). The homology between V(L) and V(H) regions of antibody BS-5 (28%) is not greater than that observed between the V(H) region of antibody BS-5 and the V(L) regions of different rabbit antibodies.

Affinity labelling of the binding site of rabbit antibody. Evidence for the involvement of the hypervariable regions of the heavy chain

The binding sites of rabbit antibodies with affinity for the haptenic group 4-azido-2-nitrophenyl-lysine have been specifically labelled by photolysis of the hapten-antibody complex. The extent of covalent labelling was 0.5-0.9mol of hapten bound/mol of antibody and, by using an immunoadsorbent, antibody with 1.3mol of hapten/mol was obtained. The antibody was specifically labelled in the binding site and the ratio of labelling of heavy and light chains was in the range 3.3-5.0. The labelled heavy chains were cleaved by CNBr treatment and after reduction and alkylation of the intrachain bonds, were digested with trypsin. Evidence is presented that two regions of the heavy chain, positions 29-34 and 95-114, together contain about 80% of the label on the heavy chain; these two regions respectively include two of the hypervariable regions of rabbit heavy chain.

Amino acid sequence of the N-terminal sixty-nine residues of heavy chain derived from a homogeneous rabbit antibody

The sequence of the N-terminal 69 residues of heavy chain from a homogeneous rabbit antibody to type III pneumococcal polysaccharide was determined. The sequence is similar to that found in heavy chains of normal pooled rabbit immunoglobulins of the same allotype Aa1. Two regions of the homogeneous heavy chain (residues 35-46 and 62-69) are very similar to corresponding regions of heavy chains from rabbit Aa2 immunoglobulin, as well as from mouse, guinea-pig and human immunoglobulins. In contrast, residues 47-62 appear to be variable. Comparison in this section with another homogeneous anti-pneumococcal antibody (Strosberg et al., 1972) of related specificity and of the same allotype indicates sequence variation in at least three positions. An antibody to group C streptococcal carbohydrate of allotype Aa2 (Fleischman, 1971) differs by five amino acids in the same region of the heavy chain. Sequence variability between these three antibodies does not occur in homologous positions within this variable section. Allotype-related sequences could not be identified in section 34-65.

The antibody binding site. Labelling of a specific antibody against the photo-precursor of an aryl nitrene

The isolation of specific rabbit antibodies for the haptenic group 4-azido-2-nitrophenyl, is described. These antibodies bind 1.8-2.0mol of hapten [in-(4-azido-2-nitrophenyl)-l-lysine]/mol with an association constant of nearly 10(7)m(-1) at 4 degrees C. On photolysis of the antibody-hapten complex, resulting in the formation of an aryl nitrene at the binding site, hapten was covalently bound to the antibody, and the antibody binding site was blocked. The ratio of labelling of heavy- and light-chains was 2.5:1. Two small peptides were isolated from digests of labelled heavy-chain, indicating that some 13% of the label in the antibody was attached to cysteine-92 and to alanine-93. These residues are adjacent to the major hypervariable region in rabbit heavy-chain (residues 95-105).

Amino-acid sequences of light chains of a rabbit anti-p-azobenzoate antibody

Half-cystine peptic peptides representing the intrachain disulfide bonds of the light chain from an apparently homogeneous rabbit anti-p-azobenzoate antibody were isolated in good yields after reduction and alkylation with [(14)C]iodoacetate, and their sequences were determined. The sequence of the first 21 amino-terminal residues was also determined. The good yields of these peptides, the fact that no variants of any of them were found, and the cleanness of the amino-terminal sequence determination confirm the high degree of homogeneity of this light-chain preparation. Previous evidence for the homogeneity of the light chain includes the appearance of only a single band upon analysis by disc electrophoresis, a relatively unique amino-acid composition, and a simple tryptic peptide map. The whole antibody shows a homogeneity of the hapten-binding constant. The antigen used in the present work is complex, since the attached hapten groups are in a large variety of environments, particularly since the carrier is a heterogeneous mixture of globulins. The very limited heterogeneity of the antibodies found in this case would appear to depend on the stimulation of only a few of the cells capable of producing antibody against a given hapten, rather than on a structural identity of the environment around each individual hapten group that is located on the antigen molecule.

Localization of two additional hypervariable regions in immunoglobulin heavy chains

Cyanogen bromide fragments were isolated from the heavy chains of three human IgG myeloma proteins of the V(H)III subgroup, sequenced by an automated method, and localized to the variable region. Inspection of these sequences, together with corresponding stretches from both human and animal proteins (studied in other laboratories) led to the detection of two additional hypervariable regions characteristic of the V(H) segment of immunoglobulin heavy chains. These areas of hypervariability, involving heavy-chain residues 86-91 and 101-109, were separated by a region of relative constancy. The close relationship of these two hypervariable regions, and the previously described first heavy-chain hypervariable region (residues 31-37), to the first heavy-chain disulphide bridge implies that the three hypervariable areas might be in close steric approximation in native immunoglobulin molecules. Examination of the sequences of the terminal portion of V(H) of all these proteins (the segment from residue 95 to the beginning of homology region C(H)l) revealed that no subgroup-specific residues could be identified in this area. Thus, heavy-chain subgroup distinctions may not extend through the entire variable region.

Allotypically related sequences in the Fd fragment of rabbit immunoglobulin heavy chains

The sequence has been completed of the N-terminal 94 residues of the variable section of the Fd fragment of heavy chains from rabbit immunoglobulin G (IgG) of allotype As1. Most of the sequence of the same section from IgG of allotype Aa3 is also reported. These results, in conjunction with a substantial sequence of the variable region of allotype Aa2 reported elsewhere (Fleischman, 1971), show the presence of 16 positions (including six consecutive positions) in which the residue present correlates with the allotype. No allotype-related sequence variation has been found in the constant section of the Fd fragment. This evidence supports the view that two genes code for the heavy chain and it can be used as evidence in favour of somatic mutation as the origin of the variability in the sequence of the N-terminal section. The evolutionary origin of the ;a' locus allotypes of rabbit immunoglobulins remains obscure.

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.

Structural basis of the A14 and A15 allotypic specificities in rabbit immunoglobulin G

The structural basis for the A14 and A15 allotypic specificities of rabbit immunoglobulin G was investigated with Fe fragments prepared from homozygous rabbits. The presence of threonine in the Cgamma2 region (position 309: Eu numbering) correlates with the A14 allotype; the presence of alanine at this same position correlates with the A15. Now that the sequence of the Cgamma2 region of rabbit IgG has been completely elucidated, a high degree of homology of the constant region domains of rabbit and human gamma chains is apparent (about 60-80%).

Heavy-chain variable regions in normal and pathological immunolobulins

Aminoacid sequence analysis of immunoglobulin G heavy chains from each of 15 normal individuals showed the presence of VHIII subgroup sequences in all individuals, to an extent of about 15-25% of the total. Therefore, different subgroups of the heavy-chain variable region are not products of alleles of a single gene.N-terminal aminoacid sequences were determined for ten heavy chains of myeloma proteins that belonged to the VHIII subgroup. Our results demonstrate the existence of a "hypervariable" region of sequence between positions 30 and 35, homologous to one of the three hypervariable regions of light chains. At several positions, variants of the basic sequence are repeated in different proteins. It is likely that such variants are derived from several recently evolved genes that constitute the VHIII subgroup.