High resolution isoelectric focusing of immunoprecipitated proteins under denaturing conditions. A simple analytical method applied to the study of complement component polymorphisms

Mechanisms of thermoinactivation of endoglucanase I from Trichoderma reesei QM 9414

The mechanism of irreversible thermoinactivation of endoglucanase I from Trichoderma reesei has been determined at 70 degrees C at the pH of maximum enzyme activity. The time-course of thermoinactivation did not follow first-order kinetics and kinetic constants of the process were dependent on enzyme concentration, suggesting that aggregation was the main process leading to irreversible inactivation. The enzyme was extremely resistant to urea, which in fact seemed to stabilize it against temperature. Disulphide exchange, deamidation and hydrolysis of peptide bonds were also responsible for the loss of enzyme activity at 70 degrees C.

Polymorphism and deficiency of human factor H-related proteins p39 and p37

We described previously cDNA clones representing a novel factor H-related 1.4 kilobase mRNA. This mRNA species codes for a doublet of serum proteins of M(r) 39,000 and 37,000 (p39/p37). The respective recombinant proteins of the three clones H-69, pFH1.4a, and pFH1.4b differ in the expression of the epitope recognized by the monoclonal antibody (mAb) 3D11. This probably reflects the difference of three amino acid residues of the deduced protein sequence. Here we report evidence for corresponding alterations in the native proteins p39/p37 in human sera. Employing mAb 3D11 and a polyclonal factor H-specific antiserum we detected three different patterns in western blot analyses of human sera which we provisionally termed FH1.4p+m+, FH1.4p+m-, and FH1.4p-m-. In the first pattern, p39/p37 were recognized by both antibodies, while in the second pattern the two proteins reacted only with the polyclonal antiserum. Both antibodies failed to detect p39/p37 in the third pattern. These phenotypes are found in the healthy population with frequencies of 0.556, 0.40, and 0.044, respectively. The frequencies of the alleles FH1.4*p+m+, FH1.4*p+m-, and FH1.4*p-m- were estimated to be 0.33, 0.46, and 0.21, respectively, assuming the gene distribution to be in Hardy-Weinberg equilibrium. Studies of 98 members from 27 families revealed an autosomal Mendelian inheritance. Southern blot data support our assumption of a polymorphism of the factor H-related proteins p39 and p37.

Epstein-Barr virus/complement fragment C3d receptor (CR2) reacts with p53, a cellular antioncogene-encoded membrane phosphoprotein: detection by polyclonal anti-idiotypic anti-CR2 antibodies

Epstein-Barr virus and the C3d fragment of the third component of complement are specific extracellular ligands for complement receptor type 2 (CR2). However, intracellular proteins that react specifically with CR2 and are involved in post-membrane signals remain unknown. We recently prepared polyclonal anti-idiotypic anti-CR2 antibodies (Ab2) by using the highly purified CR2 molecule as original immunogen. We showed that Ab2 contained anti-idiotypic specificities that mimicked extracellular domains of CR2 and detected two distinct binding sites on CR2 for its specific extracellular ligands, Epstein-Barr virus and C3d. We postulated that Ab2 might also contain specificities that could mimic intracellular domains of CR2. Here we report that Ab2, which did not react with Raji B-lymphoma cell surface components, detected specifically, among all components solubilized from Raji cell membranes, a single intracellular membrane protein of apparent molecular mass of 53 kDa. This protein was identified as the p53 cellular antioncogene-encoded membrane phosphoprotein by analyzing its antigenic properties with Pab1801, a monoclonal anti-p53 antibody, and by comparing its biochemical properties with those of p53. Additionally, solubilized and purified CR2 bound to solubilized p53 immobilized on Pab1801-Sepharose. p53, like CR2, was localized only in purified plasma membranes and nuclei of Raji cells. These data suggest strongly that p53, a cellular antioncogene-encoded phosphoprotein, reacted specifically with CR2 in Raji membranes. This interaction may represent one of the important steps through which CR2 could be involved in human B-lymphocyte proliferation and transformation.

Production of a monoclonal antibody directed against an interferon-induced 56,000-dalton protein and its use in the study of this protein

Interferon (IFN) treatment of cells induces the synthesis of several new proteins. A hybridoma cell line producing monoclonal antibody to the IFN-induced 56,000-dalton protein has been developed. The IFN-induced 56,000-dalton protein is synthesized by a variety of different cells and in response to IFN-alpha, IFN-beta, and IFN-gamma. The induction of this protein is dependent on de novo RNA synthesis, since its induction is inhibited if actinomycin D and the IFNs are added to the cells simultaneously. Labeling of IFN-treated cells at 4-h intervals at various times after the addition of the IFNs reveals that the synthesis of the 56,000-dalton protein in IFN-alpha-treated cells peaks within 12 h after the addition of the IFN and is no longer enhanced 20 h after exposure to the IFN. In contrast, IFN-gamma-treated cells continue to show an enhanced synthesis of this IFN-induced protein even after 20 h of exposure to the IFN. Thus, the synthesis of the IFN-induced 56,000-dalton protein is regulated differently by the different IFNs. When cells are treated with IFN-alpha or IFN-gamma in the presence of cycloheximide, and actinomycin D is added prior to the removal of the cycloheximide, the cells produce the IFN-induced 56,000-dalton protein and develop an antiviral state in response to both IFN-alpha and IFN-gamma. These results demonstrate that the synthesis of the 56,000-dalton protein is not dependent on the synthesis of an intermediary protein and that the establishment of an antiviral state occurs in the absence of multiple transcriptional events.

Ribonuclease-RNAase inhibitor complex from rat testis. Purification of the RNAase inhibitor

The RNAase inhibitor from rat testis has been purified to homogeneity. The purified protein appeared as a single spot after two-dimensional electrophoresis. The calculated Mr value is 48,000 which coincides with that obtained for the native protein on gel filtration chromatography, thus indicating a single polypeptide chain. The amino acid composition and the characteristics of the inhibitor activity are reported and compared to those of other RNAase inhibitors from mammalian tissues. The naturally occurring ribonuclease-RNAase inhibitor complex from rat testis has also been studied and compared with the rat testis inhibitor-RNAase A as model complex. The ribonuclease released from the natural rat testis complex showed heterogeneity of size. The significance of the rat testis ribonuclease/RNAase inhibitor system is discussed in terms of the important functionality of this organ.

Olive (Olea europea) pollen allergens--II. Isolation and characterization of two major antigens

A dialyzed extract of olive (Olea europea) pollen was fractionated by anion exchange chromatography on DEAE-Sepharose CL-6B using a discontinuous gradient of ammonium bicarbonate. The most important protein allergen was obtained from the 0.3 M fraction after gel filtration on Sephadex G-100 and separation by lentil-lectin Sepharose-4B. The major allergen of olive pollen was contained in the effluent and was designated Olea Antigen I. This material inhibited the RAST activity of 15 patients' sera that were tested. Analytical IEF demonstrated a major band at pH 5.3 and two minor ones at pH 5.6 and 5.0. When these were run into SDS-polyacrylamide gel electrophoresis in a second dimension, all were separated into two bands of mol. wt 17 and 19 K. A second protein, which is the next most important allergen, Olea Antigen II, was obtained from the 0.5 M fraction by chromatofocusing in a 4-7 pH range followed by filtration on Bio-gel P-30. Olea Antigen II had a mol. wt of 8 K as assessed by SDS-PAGE. IEF analysis displayed one main band at pH 3.6 and two minor bands at pH 3.8 and 4.0, respectively. OL-1, an anti-Olea europea monoclonal antibody (MAb) previously reported by us Lauzurica et al. (1988) reacted with the 17 and 19 K antigens from the crude extract and with Olea Antigen I but not with Olea Antigen II.

Serologic and biochemical analysis of HLA B15 and B5 complexes

Charge heterogeneity of HLA-B15 and HLA-B5 complexes was analyzed by one-dimensional isoelectric focusing (1D-IEF). Frozen peripheral blood lymphocytes were metabolically labeled with 35S methionine. The class I antigens were immunoprecipitated with monoclonal antibody 4E, which detects a determinant shared by HLA-B locus and Aw19-complex antigens. The desialated 1D-IEF banding patterns were correlated to microcytotoxicity data of a panel of donors from a variety of racial groups. Serologic analysis indicated the presence of specific variants: Te76, Te78, and Te79. 1D-IEF analysis clearly showed polymorphism in the B15 and B5 complexes. The Bw62 associated variant Te79 exhibited bands distinct from Bw62. One Bw62 typed donor produced a band that was different from other Bw62 typed cells. A migration pattern difference was discovered between blacks and Caucasians that were typed Bw57. Investigated antigens included HLA-B35, w46, 51, w52, w53, w57, w58, w62, w63, w70, Te76, Te78, and Te79.

Molecular characterization by high-resolution isoelectric focusing of the products encoded by the class II region loci of the major histocompatibility complex in humans. I. DR and DQ gene variants

We describe a new approach to the analysis of the structural polymorphism of the DR beta, DQ alpha, and DQ beta polypeptide chains of human histocompatibility class II antigens. In comparison to conventional two-dimensional gel studies, this method provides sharper definition of the protein bands and side-by-side comparisons within the same gel, thereby permitting the detection of minor differences in the isoelectric points of the protein chains. Using this methodology we have analyzed the IEF polymorphism and the variability in the number of the DR beta chains encoded by different DR haplotypes. Twenty DR beta chain variants, which include the products of no less than two separate DR beta loci, have been thus far identified. Alleles at one of these loci are assumed to code for DR beta chains carrying the DR alloespecificities DR1, DR2, DR3, DR4, DR5, DRw6, DR7, and DR8. Alleles at a second DR beta locus encode DR beta chains that may be shared by serologically DR-different haplotypes and carry supertypic serologic specificities (i.e., DRw52 and DRw53). We also demonstrate here that the structural polymorphisms of the DQ alpha and DQ beta chains are more extensive than previously thought, report the characterization of 14 DQ beta variants, and define their relationship to the previously described DQw serologic specificities. In addition, we describe the class II haplotype associations observed for the different DR and DQ variants characterized.

Decay-accelerating factor. Genetic polymorphism and linkage to the RCA (regulator of complement activation) gene cluster in humans

We have investigated the genetic relationships between the human decay-accelerating factor (DAF) and a group of complement components including the C3b/C4b receptor (CR1), C4-binding protein (C4bp), and factor H (H), to which DAF is structurally and functionally related. CR1, C4bp, and H were previously demonstrated to be encoded by a cluster of closely linked genes, which we have designated regulator of complement activation (RCA). Southern blot analysis of genomic DNA using a DAF cDNA probe unraveled the existence of restriction fragment length polymorphism (RFLP) for both Bam HI and Hind III restriction endonucleases. Segregation analysis of these polymorphic fragments in families informative for the segregation of alleles at the CR1, C4BP, and H loci (RCA-haplotypes), demonstrated that, in humans, the gene encoding DAF is located within the RCA gene cluster. No recombinants between DAF and C4BP/CR1 were encountered in 32 informative meioses. In addition, in two individuals showing recombination between the CR1/C4BP and H loci, DAF segregated with the CR1/C4BP segment. Thus, the DAF gene maps closer to the CR1/C4BP loci than to the H gene, from which it can be separated by genetic recombination.

Quantitative variations of the C3b/C4b receptor (CR1) in human erythrocytes are controlled by genes within the regulator of complement activation (RCA) gene cluster

The genetic relationships of quantitative and structural variations of the C3b/C4b receptor (CR1) in human erythrocytes have been analyzed in informative families. Our results demonstrate the existence of multiple discrete quantitative variations of CR1 controlled by a locus, C3bRQ, closely linked to the CR1 structural locus, C3bR. Since the amounts of CR1 produced by each C3bR allele are shown to be independently regulated, we propose that a cis-acting genetic mechanism controls the level of expression of the C3bR alleles, and that this quantitative control plays a major, if not the sole, role in determining the total amounts of CR1 on normal human erythrocytes.

Human genes for three complement components that regulate the activation of C3 are tightly linked

A new cluster of complement component genes, including C4BP, C3bR, and FH, is described. Family segregation data indicate that FH is linked to the genes for C4-bp and C4bR, previously reported to be linked and to maintain linkage disequilibrium. This cluster is not linked to the major histocompatibility complex, which contains the genes for the complement components, C4, C2, and factor B, or to the C3 locus. These data further suggest that the organization of genes for functionally related proteins in clusters may be a rule for the complement system.

Does the mouse C4-binding protein gene (C4BP) map in the H-2 region?

A previous study on the genetics of mouse C4-binding protein (C4-bp) indicated the existence of a genetic polymorphism. Two genetic variants were reported and their segregation used to determine the mapping position of the C4BP locus to the H-2D-Qa interval of the mouse H-2 system. We show here, however, that purified C4-bp does not display the previously reported polymorphism. The mapping position of C4BP in the mouse therefore remains undetermined.

Evidence for linkage between the loci coding for the binding protein for the fourth component of human complement (C4BP) and for the C3b/C4b receptor

Three pedigrees informative for the segregation of genetic variants of the binding protein for the fourth component of complement (C4BP) and C3b/C4b receptor (C3bR) have been identified. There were 10 informative meioses with no recombinants, indicating a close linkage between the loci encoding C4BP and C3bR, C4BP and C3bR [maximum lod (logarithm of odds of linkage) score: 2.4 at recombinant fraction = 0.0]. In addition, in the four unrelated individuals who were doubly heterozygous (C4BP*1, C4BP*2, C3bR*A, C3bR*B), the infrequent allele C4BP*2 segregated together with the uncommon allele C3bR*B, supporting the hypothesis of linkage between C4BP and C3bR and suggesting that linkage disequilibrium exists between these particular alleles. We conclude that the loci encoding C3bR and C4BP, two functionally related molecules, are linked.