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PubMed1986

Impaired humoral immune response in complement C3-deficient guinea pigs: absence of secondary antibody response.

A recently described genetically controlled C3 deficiency (C3D) in guinea pigs (GP) provided a unique model for studying the role of C3 in the afferent limb of the humoral immune response in a direct manner. These C3D animals, which have only 5-7% of normal serum C3 level, were immunized with the bacteriophage phi chi 174, a T cell-dependent antigen, followed by a booster injection after 4 weeks (1.5 X 10(9) plaque-forming units/kg). The formation of IgM and IgG antibody in the course of the primary and secondary response was determined and compared with a control group of inbred strain 2 GP. The C3D animals showed a markedly diminished antibody response to this antigen. Amplification of the antibody titer as well as regular isotype switching from IgM to IgG was absent in the secondary response. Increasing the amount of antigen to a high dose (1 X 10(10) plaque-forming units/kg) led to a normalization of the antibody response. The impairment in antibody formation resembles closely the impaired antibody response in C4-deficient or C2-deficient GP, which both have a block in activation of C3 via the classical pathway. However, in contrast to C4D GP or C2D GP the C3D GP do not exhibit serological characteristics of immune complex disease. They have normal levels of total serum IgM, of IgM anti-2,4-dinitrophenyl antibodies and of IgM rheumatoid factors.

Animals↗
PubMed1989

The acquired C1-INH deficiencies with autoantibodies (AAE type II).

A new type of acquired C1-inhibitor (C1-INH) deficiency has been recognized (AAE type II) which is characterized by the presence of autoantibodies to C1-INH and by a circulating 96 KD C1-INH molecule. The clinical manifestations and biochemical abnormalities of this novel autoimmune disease resemble those found in the other forms of acquired C1-INH deficiency (AAE type I), including recurrent angioedema and low serum levels of C2, C4, C1, C1q and C1-INH activity. However, in contrast to AAE type I, AAE type II is not associated to other diseases. Evidence has been provided that the anti-C1-INH antibodies play a major role in the development and maintenance of AAE type II. These autoantibodies seem to impede C1-INH activity, thus allowing unopposed activation of the complement and/or contact system and to induce the generation of the 96 KD C1-INH species in the patients' plasma.

Angioedema↗
PubMed1981

Antibody-independent interactions between Escherichia coli J5 and human complement components.

With the characterization of an increasing number of molecules that are capable of activating the 1st component of the classical pathway of complement (C), the possibility that some Gram-negative bacteria may activate C1 independent of naturally occurring antibody has been reexamined. We have confirmed a previous report that purified C1 (the activated form of C1) can bind to certain strains of bacteria and it retains its enzymatic activity when thus bound. The availability of purified C1 in its precursor form has allowed us to extend these observations to the native C1 molecule. Using a semirough mutant of Escherichia coli, the galactose epimerase-deficient strain E. coli J5, we have examined the binding and activation of radiolabeled C1. J5 bound radiolabeled C1 in a dose-dependent manner and essentially all of the bound C1 was activated as judged by SDS-PAGE. The bacteria-C1 complex consumed purified C4 and C2 and the consumption of C2 was proportional to the C4 concentration. Subsequent addition of terminal C components C3-9 supplied as serum-EDTA caused a highly significant decrease in bacterial viability. These results demonstrate that C1 may bind to the bacterial membrane in such a manner as to initiate a bactericidal reaction. Therefore, antibody-independent binding and activation of C1 must be considered in the assessment of serum sensitivity of Gram-negative bacteria.

Animals↗
PubMed1991

Defined chemically cross-linked oligomers of human C-reactive protein: characterization and reactivity with the complement system.

Chemically cross-linked C-reactive protein (CRP) oligomers were prepared and characterized, and C1q binding and C activation were investigated. Purified human CRP was polymerized in the presence of both non-cleavable and cleavable cross-linking agents and further separated by Superose 12 analytical FPLC column chromatography into fractions of 110 KDa (pentameric monomers), 220 KDa (dimers) and 330 KDa (trimers); virtually no larger oligomers were formed under a variety of experimental conditions. CRP subunits were cross-linked both within and between CRP pentamers. CRP trimers retained native CRP antigenicity without expression of neo-CRP epitopes. CRP trimers showed maximal binding and CRP dimers showed partial binding of solid phase C1q while CRP monomers bound virtually no C1q at all; CRP trimers also bound to fluid phase C1q. Binding was Ca++ independent and increased as the ionic strength or pH were lowered, characteristics comparable to binding of aggregated IgG to C1q; it was not inhibited by phosphorylcholine. CRP trimers consumed total C, C1 and C2 haemolytic activities upon incubation in fresh human serum, but much less efficiently than did CRP-protamine complexes or Agg-IgG. CRP trimers failed to deplete alternative C pathway haemolytic activity at all. The stable, chemically defined CRP oligomers described in this report, which bind C1q efficiently but display poor ability to activate the classical C pathway in the absence of an appropriate ligand, should be valuable in further studies of the interactions between CRP and the C system.

C-Reactive Protein↗
PubMed1995

A monoclonal antibody that blocks the complement regulatory activity of guinea pig erythrocytes and characterization of the antigen involved as guinea pig decay-accelerating factor.

MCA44 is a mAb with the capacity to sensitize neuraminidase-treated guinea pig E for hemolysis by homologous guinea pig C, and the Fab fragments of this mAb could also sensitize guinea pig E interfering with the function of a membrane inhibitor of C on guinea pig E. Using an immunosorbent column to which MCA44 was coupled, the antigenic molecule termed 44Ag was purified from the glycoprotein fraction extracted from E membranes. C intermediate sheep E treated with guinea pig C1 and C4 after sensitization with Ab (EAC14b cells) lost the ability to generate C3 convertase with C2 after incubation with 44Ag. Treatment of guinea pig E and PBL with phosphatidyl-inositol specific phospholipase C (PIPLC) partially removed 44Ag, as determined by flow cytometric analysis after immunofluorescence staining with MCA44. However, 125I-labeled 44Ag adsorbed to human E was efficiently removed by PIPLC treatment with a slight reduction in M(r). The 44Ag purified on an immunosorbent column showed three bands on SDS-PAGE. However, partial N-terminal amino acid sequences of the 55-kDa, 70-kDa, and 88-kDa bands under nonreducing conditions were identical and the sequence was 55% homologous to the N-terminal sequence of human decay accelerating factor (CD55). Intracutaneous administration of MCA44 or its F(ab')2 fragment resulted in increased capillary permeability, even after 3 days, as determined by the appearance of Evans blue spots after i.v. administration of the dye. Because control Abs including anti-class I-MHC did not cause such increased capillary permeability, the increase in permeability caused by MCA44 was likely induced by blocking the function of 44Ag in vivo, indicating a crucial role for these molecules in preventing over-activation of C at the site.

Amino Acid Sequence↗
PubMed1995

C3 is activated in hereditary angioedema, and C1/C1-inhibitor complexes rise during physical stress in untreated patients.

Seven patients with hereditary angioedema (HAE) were studied to understand further how physical exercise may induce attacks. The most pronounced differences between patients and controls, however, were independent of the controlled bicycle run (mean values in patients/ controls); C4(g/L): 0.12/0.28 (P = 0.0122); C4bc (AU/ml): 137.0/18.0 (P = 0.0002); C4d (mg/mL): 5.03/2.35 (P = 0.0004); C3bc (AU/ml): 8.4/6.3 (P = 0.0049); C3a (AU/ml): 11.1/5.6 (P = 0.0102). The ratio C4bc to C4 was 1141 versus 64. Consequently, a substantial part of the low amount of C4 left in HAE patients consists of activation products, and the authors show for the first time that a mild but significant activation of C3 occurs in HAE. The two HAE patients treated with danazol had values of C1-INH function and antigen, C4, and C2 in-between those of normal and untreated patients, and lower levels of split products from C4 and high molecular weight kininogen than untreated patients. As a result of the exercise, fibrinolysis increased significantly in both patients and controls, while C1/C1-INH complexes rose significantly only in the five HAE patients without treatment when compared to the seven controls (P = 0.0089). This study thus suggests that complement activation is enhanced in untreated HAE patients following physical stress.

Angioedema↗
PubMed1994

Genetics of the serine cycle in Methylobacterium extorquens AM1: identification, sequence, and mutation of three new genes involved in C1 assimilation, orf4, mtkA, and mtkB.

In a recent paper we reported the sequence of the beginning of a serine cycle gene cluster on the Methylobacterium extorquens AM1 chromosome, containing the genes encoding serine glyoxylate aminotransferase (sgaA), hydroxypyruvate reductase (hprA), and 5,10-methylenetetrahydrofolate dehydrogenase (mtdA) (L. V. Chistoserdova and M. E. Lidstrom J. Bacteriol. 176:1957-1968, 1994). Here we present the sequence of the adjacent downstream region containing three full and one partial open reading frames. The first of the full open reading frames (orf4) remains unidentified, while the other two (mtkA and mtkB) code for the two subunits of malate thiokinase, and the fourth, a partial open reading frame (ppcA), apparently encodes phosphoenolpyruvate carboxylase. Mutants containing insertion mutations in orf4, mtdA, and mtdB all were unable to grow on C1 compounds, showing that these three newly identified genes are indispensable for the operation of the serine cycle. Mutants in orf4 were also unable to grow on C2 compounds, but growth was restored by glyoxylate, suggesting that orf4 might be required for the conversion of acetyl coenzyme A to glyoxylate.

Amino Acid Sequence↗
PubMed2002

Lupus erythematosus associated with C1 inhibitor deficiency.

We report here a patient with skin lesions of lupus erythematosus (LE) associated with a type 1 hereditary C1 inhibitor deficiency. She had not experienced any episodes of angioedema. A histological examination of the affected skin lesions demonstrated liquefaction of the basal cell layer in the perifollicule. Direct immunofluorescence staining revealed the granular deposition of IgM along the dermo-epidermal junction. Blood laboratory examinations revealed low levels of CH50, C1q, C4, C2 and C1 inhibitor, but the C3 and C5 levels were within normal limits. Similar reductions in the C1 inhibitor levels were observed in 2 out of 3 sisters. Although one sister has been asymptomatic until now, the other has suffered from SLE. The antinuclear antibody titer was negative initially, but has changed to positive. The skin lesions became pigmented following topical corticosteroid therapy, but the deficient complement component levels remained unchanged. We also reviewed 23 cases in the literature of hereditary C1 inhibitor deficiency associated with SLE, DLE, LE-like eruption, and SCLE and discussed several common characteristics such as a female predominance, a high incidence of antinuclear antibodies, cutaneous manifestations, and photosensitivity.

Complement C1 Inactivator Proteins↗
PubMed2002

FISH-mapping of rDNAs and Arabidopsis BACs on pachytene complements of selected Brassicas.

To improve resolution of physical mapping on Brassica chromosomes, we have chosen the pachytene stage of meiosis where incompletely condensed bivalents are much longer than their counterparts at mitotic metaphase. Mapping with 5S and 45S rDNA sequences demonstrated the advantage of pachytene chromosomes in efficient physical mapping and confirmed the presence of a novel 5S rDNA locus in Brassica oleracea, initially identified by genetic mapping using restriction fragment length polymorphism (RFLP). Fluorescence in situ hybridization (FISH) analysis visualized the presence of the third 5S rDNA locus on the long arm of chromosome C2 and confirmed the earlier reports of two 45S rDNA loci in the B. oleracea genome. FISH mapping of low-copy sequences from the Arabidopsis thaliana bacterial artificial chromosome (BAC) clones on the B. oleracea chromosomes confirmed the expectation of efficient and precise physical mapping of meiotic bivalents based on data available from A. thaliana and indicated conserved organization of these two BAC sequences on two B. oleracea chromosomes. Based on the heterologous in situ hybridization with BACs and their mapping applied to long pachytene bivalents, a new approach in comparative analysis of Brassica and A. thaliana genomes is discussed.

Arabidopsis↗
PubMed1998

Effect of C2-associated carbohydrate structure on Ig effector function: studies with chimeric mouse-human IgG1 antibodies in glycosylation mutants of Chinese hamster ovary cells.

The complex biantennary oligosaccharide at Asn297 of IgG is essential for some effector functions. To investigate the effect of carbohydrate structure on Ab function, we have now expressed mouse-human chimeric IgG1 Abs in Chinese hamster ovary (CHO) cells with defined defects in carbohydrate biosynthesis. We had previously shown that IgG1 Abs produced in the cell line Lec 1, which attaches a high-mannose intermediate carbohydrate, were severely deficient in complement activation, showed a slightly reduced affinity for Fc gammaRI, and had a reduced in vivo half-life. We have extended these studies by producing the same dansyl-specific IgG1 in cell lines deficient in attachment of sialic acid (Lec 2) and galactose (Lec 8). IgG1-Lec 1, IgG1-Lec 2, and IgG1-Lec 8 all showed varying reactivity with a mAb specific for an epitope in the amino terminal region of C(H)2, suggesting that the conformations of these proteins were altered by the different carbohydrate structures. Functionally, IgG1-Lec 2 and IgG1-Lec 8 were comparable to wild type with respect to in vivo half-life, affinity for Fc gammaRI, and capacity for complement-mediated hemolysis. While IgG1-Lec 2 was essentially identical to wild type in its capacity to interact with individual components of the classical complement activation pathway, IgG1-Lec 8 demonstrated equivalent maximal binding at lower concentrations and was preferentially bound by mannose-binding protein. Although IgG1-Lec 1 was deficient in activation of the classical pathway, it had a superior capacity to activate the alternative pathway. These studies demonstrate that Abs bearing C(H)2-linked carbohydrate of differing structures have different functional properties.

Animals↗
PubMed1976

Forty-eight hour ice storage of kidneys: importance of cation content.

The importance of the cation content of flush solutions used for simple hypothermic storage has been investigated in a 48 hour canine kidney preservation model. Uniformly successful 48 hour storage was achieved with solution C2. However, inclusion of procaine (0.1 Gm. per 100 ml.) in the flushing solution as in C3 produced significant kidney damage. Without procaine, Sacks solution was no better than was C2 and the latter proved significantly superior to a sodium-based solution having identical anion content and osmolarity. The magnesium content of the sodium appeared to favorably influence the outcome of the kidney storage experiments.

Animals↗
PubMed1991

C4 Chido 3 and 6 distinguish two diabetogenic haplotypes: HLA-B49, SC01,DR4,DQw8 and B8,SC01,DR3,DQw2.

The combination of the HLA complement allotypes BFS, C2C, C4AQ0 (deleted gene) and C4B1, termed SC01 complotype, usually present in the HLA-B8,DR3,DQw2 diabetogenic haplotype, has also been found in a novel "low frequency" HLA-B49,DR4,DQw8 haplotype associated with Spanish insulin-dependent diabetes mellitus (IDDM). Family studies of C4 antigenic determinants Rodgers/Chido and their specific C4d nucleotide sequences confirm that this novel haplotype bearing Chido -3, -6 is not due to a recent recombination from the common HLA-B8,DR3 haplotype bearing Chido 3,6; moreover, Chido analysis at the serological or DNA level is presently the only way to distinguish both SC01 complotypes, since BF, C2, steroid 21-hydroxylase and C4 genes do not reveal other differences by restriction fragment analysis. On the other hand, HLA-B49,SC01,DR4 is the first DR4-bearing IDDM-susceptible haplotype with a deleted C4 gene described so far and the only DR4-bearing haplotype found in the Spanish population. This report further supports the fact that extended haplotypes with deleted (or "not duplicated") genes in the class III region contain IDDM-susceptibility more often than non-deleted (or "duplicated") haplotypes in the Spanish and other Mediterranean populations.

Base Sequence↗
PubMed1982

A role for C-reactive protein in the complement-mediated stimulation of human neutrophils by type 27 Streptococcus pneumoniae.

Although C-reactive protein (CRP) has been shown to be opsonic when bound to erythrocytes, its role in bacterial phagocytosis is unclear. Chemiluminescence (CL), a measure of the metabolic stimulation of neutrophils, was used to investigate the effects of CRP and complement (C) on the interaction between phagocytes and Streptococcus pneumoniae, type 27 (Pn27). CRP binding to Pn27 was demonstrated by using radiolabeled CRP, and Scatchard analysis indicated a saturation binding of about 10(7) CRP molecules/CFU. When Pn27 was pretreated with normal human serum and added to neutrophils, the CL response observed was directly related to the number of bacteria and the amount of serum added. Although bacteria pretreated with CRP alone produced minimal CL, the addition of CRP to serum resulted in a two to 13-fold enhancement of the CL response. CRP enhancement of CL was not observed with heated serum or serum from a patient genetically lacking C2. CRP bound to Pn27 was found to cause consumption of C3 and C4 in normal human serum, indicating activation of the classical C pathway. Because CRP opsonization might provide early protection in the nonimmune host, we tested the ability of CRP to enhance opsonization in serum with markedly decreased immunoglobulin. CRP enhanced the CL response in serum from a hypogammaglobulinemic patient to between 12 and 16 times the serum control. These studies show CRP binds to Pn27 and in the presence of C enhances the opsonization of these organisms. These findings support the concept that CRP plays a protective role in bacterial infection.

Agammaglobulinemia↗
PubMed1989

Drug-induced immune-complex disease.

A range of drugs including hydralazine, isoniazid, procainamide and penicillamine cause toxic side effects which resemble systemic lupus erythematosus (SLE). Deficiencies of C1, C4 and C2 are associated with idiopathic SLE, and these defects may compromise the ability of the patient to deal with immune complexes. Immune complexes with protein as antigen, such as has been reported to be diagnostic of procainamide-induced SLE, interact more with the C4A isotype of C4 than the C4B isotype. It is shown that hydralazine, isoniazid and penicillamine inhibit the covalent binding of C4 to a complement-activating surface and that the drugs themselves become covalently bound to C4. For each of these drugs, C4A is inhibited more than C4B, and it is suggested that this is an important contributory factor in the development of the toxic side effects to these drugs involving immune-complex deposition. For procainamide, it is shown that the hydroxylamine metabolite rather than the drug itself inhibits the covalent binding reaction of C4. Hydralazine, isoniazid and procainamide are metabolised by the polymorphic N-acetyltransferase, and slow acetylators are at increased risk of drug-induced lupus. For procainamide, oxidation to the hydroxylamine form is an alternative metabolic route of increased importance in slow acetylators, and it is suggested that investigation of C4 type in susceptible patients could provide a means of identifying those at greatest risk of immunotoxicity.

Humans↗
PubMed1990

Cloning and DNA sequencing of the fbc operon encoding the cytochrome bc1 complex from Rhodobacter sphaeroides. Characterization of fbc deletion mutants and complementation by a site-specific mutational variant.

The ubiquinol: cytochrome-c oxidoreductase (cytochrome bc1 complex) is a central component of the mitochondrial respiratory chain as well as the respiratory and/or photosynthetic systems of numerous prokaryotic organisms. In Rhodobacter sphaeroides, the bc1 complex has a dual function. When the cells are grown photosynthetically, the bc1 complex is present in the intracytoplasmic membrane and is a critical component of the cyclic electron transport system. When the cells are grown in the dark in the presence of oxygen, the same bc1 complex is a necessary component of the cytochrome-c2-dependent respiratory chain. The fact that the bc1 complex from R. sphaeroides has been extensively studied, plus the ability to manipulate this organism genetically, makes this an ideal system for using site-directed mutagenesis to address questions relating to the structure and function of the bc1 complex. In the current work, the cloning and complete sequence of the fbc operon from R. sphaeroides is reported. As in other bacteria, this operon contains three genes, encoding the Rieske 2Fe-2S subunit, the cytochrome b subunit, and the cytochrome c1 subunit. Recombination techniques were used to delete the entire fbc operon from the chromosome. The resulting strain cannot grow photosynthetically, but can grow aerobically utilizing a quinol oxidase. Photosynthetic growth is restored by providing fbc operon on a plasmid, and the reappearance of the protein subunits and the spectroscopic features due to the bc1 complex are also demonstrated. Finally, a mutation is introduced within the gene encoding the cytochrome b subunit which is predicted to confer resistance to the inhibitor myxothiazol. It is shown that the resulting strain contains a functional bc1 complex which, as expected, is resistant to the inhibitor. Hence, this system is suitable for the detailed characterization of the bc1 complex, combining site-directed mutagenesis with the biochemical and biophysical techniques which have been previously developed for the study of photosynthetic bacteria.

Amino Acid Sequence↗
PubMed1992

The complement system of Calomys callosus, Rengger, 1830 (Rodentia, Cricetidae).

The complement system (C) of Calomys callosus, Rengger, 1830 (Rodentia, Cricetidae), a wild reservoir for several infectious agents in Latin America, was characterized. Sera from normal adult animals lysed sheep erythrocytes (Es) previously sensitized with rabbit serum anti-Es (Ar) in the presence of veronal-buffered saline containing 0.15 mM CaCl2 and 0.5 mM MgCl2, pH 7.4, or unsensitized rabbit erythrocytes (Er) in the presence of one-half isotonic strength veronal-buffered-saline containing 2.5% glucose, 2 mM MgCl2 and 10 mM EGTA, pH 7.4. Both hemolytic curves were sigmoidal in shape, with CH50 values of 30-40 for females and 20-30 for males. C5, determined hemolytically using the intermediate cells EsArClm4m2m3m, was approximately 4.5 x 10(8)/ml and 4.0 x 10(8)/ml for females and males, respectively. Immunochemical serum analyses by double immunodiffusion or by immunoblotting using polyclonal antisera against human C1s, C1q, C2, C3, C4, C5, C8 and factors B, I and H indicated that C. callosus C components factor B, C4 and C3 cross-reacted with the corresponding human C components. Thus, C. callosus was found to contain effective classical and alternative pathways (CP, AP) and common pathways, reasonable amounts of C5 and common epitopes in the key C components, factor B, C4 and C3, which were preserved during evolution.

Animals↗
PubMed1984

Evidence for restriction of the ability of complement to lyse homologous erythrocytes.

This research explored the possibility that a mechanism for the inhibition of C exists that is capable of restricting lysis of antibody-sensitized homologous E. The ability of C to lyse E from six species was compared by using a passive lysis system that employed E coated with B. abortus LPS and bovine antibodies specific for B. abortus. A system was developed that permitted comparisons of the hemolytic efficiencies of heterologous and homologous C target cell combinations. C from all of the species tested lysed heterologous E effectively, but homologous E were poorly lysed. Furthermore, a serum factor appeared to be involved with restriction of lysis of homologous E:LPS:Ab by heterologous C, and the restriction was specific for homologous E. Human E:LPS:Ab that were washed after incubation with CH were resistant to subsequent lysis by heterologous C. This restriction did not occur at 0 degrees C or in the absence of antibodies. Incubation of homologous C with EH:LPS:Ab resulted in consumption of C1, C2, C3, and C4, but not C5. The treated CH would lyse sheep EAC1423, but it would not lyse sheep EA, EACI, or EAC142. Late reacting C components (C5 through C9) were not detectable on EH:LPS:Ab after incubation with CH, but C4 and C3 were bound to the cells. Rat late-reacting C components (rat C-EDTA) were capable of detecting C3 convertase sites on EH:LPS:Ab that had been reacted with CH. However, homologous late-reacting components and guinea pig late-reacting components were unable to detect the C3 convertase sites.

Animals↗
PubMed1991

Genetic and physical mapping of the Rhodobacter sphaeroides photosynthetic gene cluster from R-prime pWS2.

Plasmid pWS2 is an R68.45 chimera originally isolated as an R-prime which complemented the Rhodobacter sphaeroides bch-420 allele. Our experiments have shown that pWS2 is also able to complement a wide range of R. sphaeroides pigment and photosynthetic mutants employing nitrosoquanidine, transposon or insertion-generated mutations effecting puhA, puc, puf, cycA, bch, and crt genes. A combination of orthogonal-field-alternation gel electrophoresis, transverse alternating field gel electrophoresis, and conventional electrophoresis have been used to estimate the size of pWS2 at congruent to 168.3 +/- 3.5 kb. A restriction map of the congruent to 109 kb of R. sphaeroides insert DNA was generated by partial and complete restriction endonuclease digestion coupled with Southern hybridization analysis using either gene-specific or junction fragment probes. Genes encoding bacteriochlorophyll (Bchl)-binding proteins (pufBALMX, pucBA, and puhA), cytochrome c2 (cycA), and enzymes involved in Bchl (bch) and carotenoid (crt) biosynthesis have been shown to reside within a contiguous 53-kb region of the R. sphaeroides DNA present on pWS2. The puf operon lies at one end of the 53-kb segment, while the genes puhA, cycA, and pucBA, the latter two of which are located within congruent to 12.0 kb of each other, define the other end of this 53-kb region. The genetic and physical mapping data provided in this paper are discussed in terms of the similarities and differences in the organization of the photosynthetic gene cluster between R. sphaeroides and other photosynthetic bacteria as well as highlighting the use of pWS2 in studies of photosynthetic gene structure and function.

Blotting, Southern↗