Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 30
Filter
Add more filters











Publication year range
3.
Can J Biochem ; 57(6): 758-67, 1979 Jun.
Article in English | MEDLINE | ID: mdl-113060

ABSTRACT

The amino acid sequences of most of the CH1, CH2 and CH3 domains of IgG Zie, a myeloma protein belonging to the IgG2 subclass, are presented. These data make possible a comparison of the sequences of residues 253-446 of all four subclasses of immunoglobulins: these residues make up almost the entire Fc regions. A comparison can also be made of the CH1 domain of IgG1 Eu and the CH1 domain of IgG2 Zie. Earlier sequence analyses of the Fc regions of subclass 1 and 3 proteins, and parts of the Fc regions of subclass 2 and 4 proteins showed that about 95% of these sequences were identical. The extended comparisons made possible by the data presented here show that this very high degree of identity is maintained throughout the four subclasses. Similarly, the CH1 domains of gamma 1 and gamma 2 chains were found to have about 93% sequence identity. It is unlikely that the few single amino acid changes within the constant region domains can account for the marked differences between subclasses observed in the region domains can account for the marked differences between subclasses observed in the biological effector functions of immunoglobulin Fc regions, especially since most of the changes are highly conservative. Rather, it seems probable that these functional differences are caused by conformational differences between the subgroups, which result from sequence differences in the hinge regions.


Subject(s)
Immunoglobulin G , Immunoglobulin Heavy Chains , Myeloma Proteins , Amino Acid Sequence , Humans , Protein Conformation
6.
J Immunol ; 119(2): 540-2, 1977 Aug.
Article in English | MEDLINE | ID: mdl-301895

ABSTRACT

Facb fragments of rabbit anti-allotype antibody were prepared by plasmin digestion and isolated by gel chromatography. The antibody preparation was used in an attempt to induce allotype suppression in newborn rabbits. The Facb fragments were found to be ineffective in inducing the allotype suppression. Administration of Facb fragments caused a "burst" of immunoglobulin synthesis almost immediately after the administration of the antibody. It was concluded that the CH3 domain, which is responsible for the cytophilic activity of the antibody, is essential in induction of allotype suppression.


Subject(s)
Antibodies, Anti-Idiotypic , Immunoglobulin Allotypes , Immunoglobulin Fc Fragments , Immunoglobulin G , Immunosuppression Therapy , Animals , Animals, Newborn , Antibodies, Anti-Idiotypic/administration & dosage , Immunochemistry , Immunoglobulin Fragments/isolation & purification , Rabbits
7.
Biochem J ; 157(3): 535-40, 1976 Sep 01.
Article in English | MEDLINE | ID: mdl-791267

ABSTRACT

The digestion of human IgG1/K myeloma proteins with pepsin in the presence of 8 M-urea produces fragments that differ from those produced by aqueous peptic digestion, and from other characteristic immunoglobulin fragments. Fb'2, the larger urea/pepsin fragment, was previously shown to consist of the constant regions of the light chains, and the CH1 domains and hinge regions of the heavy chains. The smaller fragment, upFc, has now been characterized. After reduction, three peptides were released from fragment upFc. Amino acid sequencing, N- and C-terminal determinations and amino acid compositions have enabled these peptides to be identified as residues Ile-253 to Leu-306, residues Thr-307 to Asp-376 and residues Thr-411 to Gly-446 of the heavy chain. Fragment upFc therefore contains the entire Fc region, beginning at residue Ile-253, except for a 34-residue section from within the CH3-domain disulphide loop. Peptic digestion of IgG1/K proteins in 8M-urea therefore provides a method for isolating from gamma1 heavy chains five homogeneous peptides in good yield, which account for almost the entire constant region. Characterization of fragments Fb'2 and upFc has shown that the action of pepsin in urea is entirely different from that of aqueous pepsin. Two gamma1 heavy chains have been shown to differ in sequence at three positions from the sequence reported for protein Eu.


Subject(s)
Immunoglobulin Fc Fragments/analysis , Immunoglobulin G/analysis , Amino Acid Sequence , Amino Acids/analysis , Humans , Myeloma Proteins/analysis , Pepsin A , Peptide Fragments/isolation & purification , Urea
8.
Biochem J ; 155(1): 31-6, 1976 Apr 01.
Article in English | MEDLINE | ID: mdl-779769

ABSTRACT

The digestion of a human IgG1 K myeloma protein with pepsin in the presence of 8M-urea was observed to produce a fragment, designated Fb'2, which differed from the products of aqueous peptic digestion and from other characteristic immunoglobulin digestion products. 2. Fragment Fb's was also found when two other IgG1/K proteins were treated similarly. 3. Sedimentation-equilibrium studies showed the mol.wt. of fragment Fb'2 to be 56800. 4. On reduction, two equivalents of each of three peptides were released from fragment Fb's; these were characterized by N- and C-terminal determinations and by amino acid sequencing. 5. Fragment Fb'2 was shown to consist of the constant regions of both light chains, from residue Ile-117 to the C-terminus, and the CH1 domains and hinge region of the heavy chains, from residue Val-113 to residue Met-252, with a gap of five residues within the intrachain disulphide loop, between residues Leu-174 and Tyr-180.


Subject(s)
Immunoglobulin Fab Fragments/analysis , Immunoglobulin G/analysis , Amino Acid Sequence , Chromatography, Gel , Electrophoresis, Polyacrylamide Gel , Electrophoresis, Starch Gel , Humans , Immunoglobulin Fragments/analysis , Molecular Weight , Myeloma Proteins/analysis , Pepsin A , Peptide Fragments/analysis , Sodium Dodecyl Sulfate , Spectrophotometry, Ultraviolet , Ultracentrifugation , Urea
9.
Can J Biochem ; 53(6): 706-12, 1975 Jun.
Article in English | MEDLINE | ID: mdl-237623

ABSTRACT

Using the phthaloyl method, 18 gamma-L-glutamyl peptides labelled with 14-C in the N-terminal position have been synthesized. The products were isolated by simple procedures using a Dowex-1 column or high voltage electrophoresis. The synthetic peptides contain minor impurities of the corresponding D-glutamyl isomers. The proportion of D-isomer was determined by the use of glutamic decarboxylase, or by a new method using digestion with purified gamma-glutamyl cyclotransferase and determination of the resulting 2-pyrrolidone-5-carboxylic acid (5-oxoproline). Evidence was obtained that gamma-glutamyl cyclotransferase acts only on the L-form of gamma-glutamyl substrates; the enzyme could, therefore, be used for preparation of gamma-D-glutamyl peptides from their racemic mixtures. The specificity of gamma-glutamyl cyclotransferase has been examined using pure enzyme prepared from pig liver, and extracts from tissues of rat and man. The basic structural requirement in substrates may be represented as gamma-L-glutamyl-NH--CHR--COOH. The amino acid linked to the gamma-glutamyl group must be in the L configuration.


Subject(s)
Acyltransferases/metabolism , gamma-Glutamylcyclotransferase/metabolism , Adult , Amino Acids/analysis , Animals , Carbon Radioisotopes , Female , Glutamates/metabolism , Glutamine/metabolism , Humans , Liver/enzymology , Male , Middle Aged , Peptides/chemical synthesis , Rats , Stereoisomerism , Structure-Activity Relationship , Swine , gamma-Glutamylcyclotransferase/isolation & purification
12.
Biochem J ; 137(2): 281-9, 1974 Feb.
Article in English | MEDLINE | ID: mdl-4824211

ABSTRACT

Normal human immunoglobulin G (IgG) was treated with radioactive N-ethylmaleimide in the absence of a reducing agent but in the presence of a denaturing solvent. The sites of reaction were determined by isolation of the radioactive peptides from thermolytic digests of the heavy and light chains. Six radioactive peptides were purified from the digest of the light chain and ten from that of the heavy chain. When sequenced, all the peptides were identical with peptides that would be predicted for the half-cystine residues involved in disulphide bonds. The specific radioactivity of the peptides indicated that the proportion of the half-cystine residues in the reduced form varied from 0.57 to 2.54%. These results indicate that the disulphide bonds of IgG are not completely oxidized. The estimate of 0.2mol of SH group/mol of IgG (Cecil & Stevenson, 1965; Luks & Connell, 1968) can be accounted for if 0.8% of every half-cystine residue of the intrachain bonds was in the reduced form. Variable cysteine residues as have been described in several myeloma proteins must occur extremely infrequently among the immunoglobulins.


Subject(s)
Immunoglobulin G , Amino Acid Sequence , Amino Acids/analysis , Carbon Radioisotopes , Chromatography, Ion Exchange , Chromatography, Paper , Cystine/analysis , Disulfides , Electrophoresis, Paper , Ethylmaleimide , Humans , Oxidation-Reduction , Peptide Fragments/analysis , Protein Conformation , Protein Denaturation , Spectrophotometry , Thermolysin
17.
Biochem J ; 123(3): 455-64, 1971 Jul.
Article in English | MEDLINE | ID: mdl-5001593

ABSTRACT

Four proteins, which have been designated A, B, C and D, have been purified from human parotid saliva. These proteins are the major constituents of parotid saliva which migrate rapidly to the anode in polyacrylamide electrophoresis at pH9.5. Gel filtration and polyacrylamide electrophoresis were employed in the purification procedures. After purification all four preparations were tested for homogeneity by electrophoresis at pH2.8 and 9.5, by isoelectric focusing in the pH range 3-10, by immunodiffusion, and by sedimentation in the analytical ultracentrifuge. None of the proteins showed significant activity in assays for amylase, acid and alkaline phosphatase, protease, lysozyme, ribonuclease, peroxidase, beta-glucuronidase, beta-galactosidase, iron-binding activity and esterase. No cross-reactions were detected with antisera specific for lactoferrin and 15 serum proteins. All four proteins were rich in glutamic acid, proline and glycine and were lacking completely the sulphur-containing amino acids. Proteins A and C contained no threonine or tyrosine. Carbohydrate could be demonstrated only in protein A at a concentration of 4% of the total protein.


Subject(s)
Proteins/isolation & purification , Saliva/analysis , Acid Phosphatase , Alkaline Phosphatase , Amino Acids/analysis , Amylases , Blood Proteins , Chromatography, Gel , Cross Reactions , Electrophoresis, Disc , Esterases , Galactosidases , Glucuronidase , Glutamates/analysis , Glycine/analysis , Humans , Hydrogen-Ion Concentration , Immune Sera , Immunodiffusion , Iron , Isoelectric Focusing , Muramidase , Parotid Gland/metabolism , Peptide Hydrolases , Peroxidases , Proline/analysis , Ribonucleases , Saliva/enzymology , Threonine/analysis , Tyrosine/analysis , Ultracentrifugation
19.
Science ; 172(3983): 574-7, 1971 May 07.
Article in English | MEDLINE | ID: mdl-4101951

ABSTRACT

The partial sequence of the light chain of the myeloma-like immunoglobulin Sac shows a large deletion in its variable region. The sequence provides evidence that the corresponding gene was formed by the repair of DNA broken at nonhomologous positions. Data from other immunoglobulin (heavy) chains containing large deletions are compatible with their genes also being the result of DNA breakage and nonhomologous repair. Single homologous reciprocal exchanges in DNA networks at immunoglobulin loci could be the cause of the nonhomologous breaks. The relevance of these events to the generation of normal antibody variability remains to be determined.


Subject(s)
Amino Acid Sequence , DNA , Immunogenetics , Peptides/analysis , gamma-Globulins/analysis , Bence Jones Protein/analysis , Crossing Over, Genetic , Immunoglobulins , Nucleic Acid Hybridization , Recombination, Genetic
SELECTION OF CITATIONS
SEARCH DETAIL