Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Complement C7”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources
PubMed1995

Complement C7 M/N allotyping in infectious diseases.

The allotypes of the C7 M/N polymorphism are determined by ELISA by comparing the reaction pattern of the allospecific monoclonal antibody WU 4-15 with that of polyclonal anti-C7 IgG. In order to find disease associations of the two alleles C7*M and C7*N we tested 528 hospitalised patients, most of them suffering from infectious diseases. No significant association of either of the two C7 M/N alleles to a particular disease was found, in particular refuting the hypothesis that Lyme borreliosis may be more frequent in homozygous carriers of the hypomorphic allele C7*N.

Alleles↗
PubMed1993

Clusterin, the human apolipoprotein and complement inhibitor, binds to complement C7, C8 beta, and the b domain of C9.

Clusterin is a heterodimeric multifunctional protein expressed in a variety of tissues and cells. It forms high density lipid complexes in plasma and participates in the control of the lytic activity of the late complement complex (TCC, C5b-9). Together with vitronectin, clusterin binds to the nascent amphiphilic C5b-9 complex, rendering it water soluble and lytically inactive. To define the interactions that underlie the complement-inhibitory function of clusterin, we have examined the binding interactions between [125I]clusterin and the isolated components of the complex, C5b-6, C7, C8, and C9 and vitronectin. By using ligand blotting in the presence of Tween, specific binding of the labeled clusterin with C7, the beta-subunit of C8 and C9 was detected. Binding to C9 was competed by polymerized C9, but not by C8, C7, C6, and CD59, suggesting that the conformational change occurring during the hydrophilic-amphiphilic transition of C9 exposes the interaction site for clusterin. When thrombin-treated C9 was analyzed, clusterin was found to recognize the C9b fragment containing the hydrophobic membrane interaction segment. Both subunits of clusterin interact with C9 and are similarly potent in inhibiting C5b-9-mediated hemolysis and Zn+(+)-induced C9 polymerization. These results show that clusterin exerts its inhibitory effect by interacting with a structural motif common to C7, C8 alpha, and C9b.

Clusterin↗
PubMed1995

Molecular basis of the complement C7 M/N polymorphism. A neutral amino acid substitution outside the epitope of the allospecific monoclonal antibody WU 4-15.

The allotypes of the C7 M/N polymorphism are determined by comparing the ELISA reaction pattern of the allospecific mAb WU 4-15 with polyclonal anti-C7 IgG. To characterize the molecular basis of this polymorphism, the WU 4-15 epitope was mapped by expression of cDNA fragments. It was found to be located within the boundary region of the two short consensus repeats of C7 (amino acid residues 595-612). Coincidentally an A or C substitution was found in the course of investigation of the gene structure at nucleotide 1759. This leads to an electrically neutral Pro/Thr substitution at residue 565 and alternative Sau961 or RsaI restriction sites, respectively. Enzymatic digestion or sequencing of PCR-amplified genomic DNA from C7 M/N-typed individuals showed a perfect correspondence of the genotype with the phenotype of the C7 M/N polymorphism. In contrast, no association was found with the genotypes of a second polymorphic site at residue 367. Thus, a threonine at amino acid residue 565 allows access of WU 4-15 to its epitope but its substitution with proline almost completely inhibits access in the native molecule, although the epitope is about 40 amino acid residues distant from the polymorphic site in the primary structure. Furthermore, the different conformational structure is probably responsible for the hypomorphic appearance of C7*N.

Alleles↗
PubMed2001

High prevalence of complement C7 deficiency among healthy blood donors of Moroccan Jewish ancestry.

The incidence of the specific component deficiencies in various ethnic groups is not known, although there appears to be an ethnic predilection for C6 and C8alpha-gamma deficiencies in blacks, whereas C7 and C8beta deficiencies are predominantly noted in Caucasians. Infectious diseases, particularly recurrent meningococcal infections, are observed more commonly with late component deficiencies. In the current study, we have simplified the PCR technique by using site-directed mutagenesis and designer primers in a cohort of Israeli Moroccan Jewish blood donors to ascertain allele frequency in this ethnic group, which, based on earlier studies, was considered to be at risk for C7 deficiency. The total mutant allele frequency in this ethnic cohort was 1.1% of a total of 365 healthy Israeli Moroccan Jews, including one homozygote. The identification of mutant alleles was efficient and inexpensive, and hence a large cohort was studied. The finding of complement deficiency identifies individuals at risk for Neisserial infections, which are known to be potentially life-threatening. Conversely, when a patient of Moroccan ancestry is diagnosed with a Neisserial infection, it is important to determine the complement status.

Blood Coagulation Disorders↗
PubMed1985

Self-association of the seventh component of human complement (C7): dimerization and polymerization.

Two association reactions of isolated C7 are described. The incubation of isolated C7 in 1% deoxycholate results in hemolytically inactive dimeric C7 that has a sedimentation coefficient of 7.3S. Dimeric C7 expressed hydrophobic domains that bound 41 +/- 4 mol deoxycholate per mol C7 and that aggregated upon removal of the detergent. The dimeric nature of the deoxycholate-treated C7 was demonstrated by analytical ultracentrifugation and by gel filtration, and yielded the following parameters: Mr = 230,000; diffusion coefficient, D = 2.9 X 10(-7) cm2/sec, and Stokes' radius, rH = 7.3 nm. Dimeric C7 exhibits an increased electrophoretic mobility and an increased beta-sheet structure, as compared with monomeric C7. Upon incubation with deoxycholate-phospholipid mixed micelles and removal of the detergent, the dimeric C7 became firmly associated with the lipid vesicles and was partially aggregated in the lipid bilayer. Trypsin treatment released approximately 50% of the protein material from the C7 vesicle complex. The other association reaction of isolated C7 occurs upon incubation with 1 M guanidine HC1; C7 forms soluble, linear protein polymers that have sedimentation coefficients ranging from 20 to 30S. The strands are 5 to 8 nm wide and vary in length between 20 to 100 nm. They tend not to aggregate, they are hemolytically inactive, and they exhibit increased beta-sheet structure, as compared with monomeric C7. They can be dissociated to hemolytically active monomers by exposure to 4 M guanidine HC1 and by subsequent 100-fold dilution with buffer. Isolated C5 or C6 did not exhibit any of these properties. The results suggest that the properties acquired by C7 in the hydrophilic-amphiphilic transition may be responsible for the expression of the membrane binding site of "metastable" C5b-7 and for the polymerization of C5b-7 within the target membrane.

Complement Activation↗
PubMed1996

The Cayapa Indians of Ecuador: a genetically isolated group with unexpected complement C7 M/N allele frequencies.

The Cayapa Indians live in north-western Ecuador in close proximity to a Black population of African ancestry. C7 M/N allotyping has proved to be a good technique for plasma genetic analysis in several populations. Investigation of 124 Cayapa plasma samples revealed the highest allele frequency of C7*N observed in any population examined so far (0.36 versus 0.225 or lower). The marked difference in frequency compared with several Oriental populations, which are believed to have been derived from the same Asian population as native Amerindians, may reflect the effect of a small founder population followed by a high degree of genetic isolation. The allele frequency of 0.12 for C7*N determined for the neighbouring Black population supports the conclusion that there has been a lack of genetic admixture of Cayapas with other populations, confirming the results of ethnohistorical investigations and other protein polymorphism studies.

Alleles↗
PubMed1999

Five new polymorphisms in the complement C7 gene and their association with C7 deficiency.

Five new polymorphisms in the C7 gene are described: 2 in intron 1, and 1 each in introns 7, 8 and 15. Four of these are single nucleotide exchanges, while the fifth is a T insertion at 10 sequential Ts. Allele frequency data are presented for intervening sequence (IVS)1+ 55 in 6 normal population groups. We present new and updated data in these populations on a previously described C7 polymorphism in exon 13 (cDNA 1792 A/T). We also report the extended haplotypes associated with C7 deficiency for which marker investigation is a useful, and in some cases vital, adjunct to the identification of the gene defects. Almost without exception, a particular haplotype is associated with a particular mutation causing the deficiency state. Haplotyping is especially useful where polymerase chain reaction failure on one chromosome could be a cause for difficulties in detecting a molecular defect due to heterozygosity for large deletions or unidentified variations at the locations of the primers.

Alleles↗
PubMedDate not supplied

[Hereditary deficiency in complement C7 and platelet aggregation disorders associated with rheumatoid arthritis. One case (author's transl)].

In a patient suffering from rheumatoid arthritis thorough investigations led to the discovery of complete deficiency in the 7th component of the complement. A study of the patient's family tree confirmed the hereditary, codominant autosomal character of the deficiency, unrelated to the HLA system. The complement-dependent serum functions were investigated: the opsonizing and chemotactic activities were preserved, but bactericidal properties were lacking. Coagulation studies showed disorders in platelet aggregation in the presence of thrombin, and these were corrected by the addition of C7. The association of a dysimmune disease with C7 deficiency is probably not fortuitous; it might result from a common gene abnormality or, in some cases, from repeated infections.

Adolescent↗
PubMed1994

Isolation of mouse complement component C7.

Mouse complement component C7 was purified from serum by a sequential procedure of fractionation precipitation by ammonium sulfate, followed by DE-52 anion exchange chromatography. Protein G affinity column chromatography, Mono S cation exchange chromatography and Superdex 200 gel filtration. The final product contained a highly purified mouse C7 component showing a single band on SDS-PAGE at the apparent Mrs of 90 kDa and 100 kDa under non-reduced and reduced conditions respectively. The yield of C7, which was measured by the biological activity, was 7.0%

Animals↗
PubMed2000

Isolation, characterization, and cloning of porcine complement component C7.

Activation of the complement system through the classical, alternative, or lectin pathway results in the formation of the terminal complement complex. C7 plays an integral role in the assembly of this complex with target cell membranes. To date, only human C7 has been cloned and characterized; thus, in this study, we characterized the porcine complement component C7. Porcine C7 was isolated by affinity chromatography as a single glycoprotein with an approximate molecular mass of 90 kDa and 100 kDa under reducing and nonreducing conditions, respectively. The full-length porcine C7 cDNA was isolated, and the predicted amino acid sequence exhibited 80% identity with human C7 with conservation of the cysteine backbone and two putative N-linked glycosylation sites. Porcine C7 mRNA expression was detected in all tissues investigated, except polymorphonuclear and mononuclear leukocytes. Addition of purified porcine C7 restored the hemolytic activity of C7-depleted human sera in a dose-dependent manner. A functionally inhibitory mAb against porcine C7 attenuated the hemolytic activity of human, rabbit, or rat sera, suggesting an important conserved C7 epitope among species. These data demonstrate that porcine and human C7 are highly conserved, sharing structural and functional characteristics.

Amino Acid Sequence↗
PubMed1988

The structure of human complement component C7 and the C5b-7 complex.

The molecular architecture of human complement component C7 was elucidated at several structural levels. The complete primary structure of C7 was derived from the cDNA sequence of clones isolated from a human liver library. C7 is a mosaic protein that consists of 821 amino acids. The amino-terminal two-thirds of C7 has 23-30% homology with complement components C8 and C9. In addition, the carboxyl-terminal third contains four cysteine-rich segments that have overlapping internal homology. The protein is a single polypeptide chain with 28 disulfide bonds and is glycosylated at two sites. Virtually all the cysteines are found in small units of 35-77 amino acids that exhibit homology with those of various proteins including the low density lipoprotein receptor, epidermal growth factor precursor, thrombospondin, and blood coagulation factors IX and X. The secondary structural analysis, estimated by circular dichroism, suggested a high content of beta-sheet (38%) and beta-turns (24%). The tertiary structure, visualized by transmission electron microscopy, indicated a flexible elongated molecule with dimensions of 151 X 59 X 43 A. The quaternary structure of the C5b-7 complex bound to lipid vesicles was observed to be in the form of monomers or dimers. The monomer C5b-7 consists of a leaflet and a long flexible stalk, and the dimer has two leaflets linked through a supercoiled stalk. Membrane binding is mediated by the stalk part of the complexes. Using a radioiodinated photoreactive cross-linking reagent bound to the polar head group of phosphatidylethanolamine, the stalk part of the C5b-7 complex could be labeled preferentially, and it was found to consist mainly of C6 and C7. Thus, C7 plays a major role in bringing about the hydrophilic-amphiphilic transition during the formation of the membrane attack complex, and it serves as a membrane anchor for the C5b-7 complex.

Amino Acid Sequence↗
PubMed1995

Genetic detection of the silent allele (*Q0) in hereditary deficiencies of the human complement C6, C7, and C9 components.

DNA polymorphisms (RFLPs) of the human complement component C6, C7, and C9 genes were studied in three C7-deficient (C7D) families, one C6-deficient (C6D) family, and one C9-deficient (C9D) family. The 3 loci are closely linked on human chromosome 5. The haplotypes carrying the "silent" allele (C7*Q0, C6*Q0, and C9*Q0) were defined in each family, allowing for the detection of carriers among asymptomatic relatives. This paper describes familial studies on a type of hereditary trait, characterized by recurrent Neisseria infections in individuals homozygous for "silent" alleles at the C6, C7, or C9 loci.

Alleles↗
PubMed2003

Cloning and characterization of human complement component C7 promoter.

To study the transcriptional regulation of the human complement component C7, a 1 kb promoter fragment was cloned and the transcription start site was determined. C7 is expressed by the hepatoma-derived cell line Hep-3B, but not by Hep-G2. Transfection of these cell lines with different C7 promoter-luciferase constructs demonstrated that 1 kb of the 5'-flanking region contains the necessary elements for driving C7 transcription in a tissue-specific manner and showed that the sequence between -29/+102 retained the majority of C7 promoter activity in Hep-3B. Electrophoretic mobility shift assays suggested that the binding of the C/EBPalpha transcription factor to a C/EBP sequence located at +42 is essential for C7 expression. To investigate whether the absence of C/EBPalpha expression in Hep-G2 cells is responsible for the lack of C7 transcription, Hep-G2 cells were transfected with a C/EBPalpha expression vector. C/EBPalpha transactivated the C7 luciferase reported gene and restored the C7 expression in Hep-G2 cells.

Base Sequence↗
PubMed1994

Hereditary deficiency of the seventh component of complement and recurrent meningococcal infection: investigations of an Irish family using a novel haemolytic screening assay for complement activity and C7 M/N allotyping.

Terminal complement component deficiency predisposes to meningococcal infection and is inherited in an autosomal co-dominant manner. An Irish family is described, in which 2 of 3 brothers had recurrent meningococcal infection. A novel screening assay was used to investigate for terminal complement deficiency and the 2 affected brothers were found to be completely deficient in the seventh component of complement (C7). Enzyme-linked immunosorbent assay for C7 revealed lower than normal levels in the remaining brother and parents. C7 M/N protein polymorphism allotyping, used to investigate the segregation of the C7 deficiency genes, showed that the apparently complement sufficient brother was heterozygous C7 deficient and a carrier of one of the deficiency genes. Complement screening should be carried out in any individual suffering recurrent meningococcal infection or infection with an uncommon meningococcal serogroup. Identification of complement deficient patients allows the implementation of strategies to prevent recurrent infection.

Adolescent↗
PubMed2004

Complement component C7 deficiency in two Spanish families.

Different genetic mutations have been described in complement component C7 deficiency, a molecular defect clinically associated with an increased susceptibility to neisserial recurrent infections. In this work we report the genetic basis of C7 deficiency in two different Spanish families (family 1 and family 2). In family 1, of Gypsy ethnical background, exon-specific polymerase chain reaction and sequencing revealed a not previously described single base deletion of nucleotide 1309 (exon 10) in the patient, as well as in her father, leading to a stop codon that causes the premature truncation of the C7 protein (K416 X 419). Additionally, the patient and her mother displayed a missense mutation at position 1135 (exon 9) located in the first nucleotide of the codon GGG (CGG), resulting in a change of amino acid (G357R). This mutation was firstly described in individuals of Moroccan Sephardic Jewish ancestry and has been also reported among Spaniards. In family 2, another novel mutation was found in homozygosity in two siblings; a two base-pair deletion of nucleotides 1922 and 1923 in exon 14 leading to the generation of a downstream stop codon causing the truncation of the C7 protein product (S620 X 630). Our results provide more evidence for the heterogeneous molecular basis of C7 deficiency as well as for the subsequent susceptibility to meningococcal disease, since different families carry different molecular defects. On the other hand, certain C7 defects appear to be prevalent in individuals from certain populations or living in defined geographical areas.

Adolescent↗
PubMed2003

Complement component C7 deficiency in a Spanish family.

Different genetic mutations have been described in complement component C7 deficiency, a molecular defect which is clinically associated with an increased susceptibility to neisserial recurrent infections, although some cases remain asymptomatic. In this work we report the genetic bases of C7 deficiency in one Spanish family. Exon-specific PCR and sequencing revealed a novel point mutation at nucleotide 615 (exon 6) leading to a stop codon (UGG to UGA) in the patient, his mother, and sister. This transversion causes the premature truncation of the C7 protein (W183X). Additionally, we detected a missense mutation at position 1135 (exon 9) located in the first nucleotide of the codon GGG (CGG), resulting in an amino acid change (G357R) in the patient, his father, as well as in his sister. This latter mutation had been previously described in individuals from Moroccan Sephardic Jewish ancestry. Since both heterozygous mutations were found in the patient as well as in his asymptomatic sister, we analyse other meningococcal defence mechanisms such as polymorphisms of the opsonin receptors on polymorphonuclear cells. Results showed that the patient and his sister bore identical combinations of FcgammaRIIA-H/R131 and FcgammaRIIIB-NA1/2 allotypes. Our results provide further evidence that the molecular pathogenesis of C7 deficiency as well as susceptibility to meningococcal disease are heterogeneous, since different families carry different molecular defects, although many of the C7 defects appear to be homogeneous in individuals from certain geographical areas. The missense mutation G357R would make an interesting topic of analysis with regard to meningococcal disease susceptibility in the Spanish population.

Base Sequence↗