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D N Cooper

Publications and source records attributed to D N Cooper.

At least 109 records · Page 6Linked to original sources
PubMed1993

L-29, an endogenous lectin, binds to glycoconjugate ligands with positive cooperativity.

The soluble mammalian lactose-binding lectins L-14-I and L-29 are both secreted and bind to oligosaccharides on laminin, a large extracellular matrix glycoprotein containing polylactosamine chains. Because of the potential functional significance of these lectin-laminin interactions, we compared quantitative aspects of L-14-I and L-29 binding to immobilized laminin using recombinant lectins labeled with 125I. We report that the concentration-dependent binding of L-29 exhibits positive cooperativity whereas binding of L-14-I does not. Cooperative binding of L-29 can also occur on glycoconjugate substrates other than laminin and is not dependent on cystine bond formation or aggregation in solution. L-29 contains repetitive sequences within the N-terminal domain not present in L-14-I. This domain is not required for binding activity, but is required for positive cooperativity. Though the precise mechanism of interaction of L-29 with laminin remains to be determined, it apparently results in assembly of a lectin aggregate on the substrate surface, which could have important functional consequences.

Animals↗
PubMed1993

Detection of missense mutations by single-strand conformational polymorphism (SSCP) analysis in five dysfunctional variants of coagulation factor VII.

Five unrelated subjects with dysfunctional coagulation factor VII (FVII) were studied in order to identify missense mutations affecting function. Exons 2 to 8 and the intron-exon junctions of their FVII genes were amplified from peripheral white blood cell DNA by PCR and screened by SSCP analysis. DNA fragments showing aberrant mobility were sequenced. The following mutations were identified: in case 1 (FVII:C < 1%, FVII:Ag 18%) a heterozygous A to G transition at nucleotide 8915 in exon 6 results in the amino acid substitution Lys-137 to Glu near the C-terminus of the FVIIa light chain; in case 2 (FVII:C 7%, FVII:Ag 47%) a heterozygous A to G transition at nucleotide 7834 in exon 5 results in the substitution of Gln-100 by Arg in the second EGF-like domain; in case 3 (FVII:C 20%, FVII:Ag 76%) a homozygous G to A transition at nucleotide position 6055 in exon 4 was detected resulting in substitution of Arg-79 by Gln in the first EGF-like domain; in case 5 (FVII:C 10%, FVII:Ag 52%) a heterozygous C to T transition at nucleotide position 6054 in exon 4 also results in the substitution of Arg79, but in this case it is replaced by Trp; case 4 (FVII:C < 1%, FVII:Ag 100%) was homozygous for a previously reported mutation (G to A) at nucleotide position 10715 in exon 8, substituting Gln for Arg at position 304 in the protease domain. Cases 1, 2 and 5 evidently have additional undetected mutations.

Amino Acid Sequence↗
PubMed1993

A novel point mutation (Val 297-->Met) in the serine proteinase domain of protein C in a patient with both venous and arterial thromboembolic disease.

A novel heterozygous GTG-->ATG (Val 297-->Met) substitution was detected in an individual with probable inherited protein C deficiency and both venous and arterial thrombotic disease. The lesion occurs in a highly conserved residue within the serine protease domain. In a molecular model of protein C, Met 297 makes unfavourable interactions with neighbouring residues suggesting that the mutant protein is unable to adopt a stable/functional conformation.

Adult↗
PubMed1993

Symptomatic type II protein C deficiency caused by a missense mutation (Gly 381-->Ser) in the substrate-binding pocket.

A patient with recurrent deep vein thrombosis and heterozygous type II deficiency, characterized by reduced protein C activity in both amidolytic and clotting functional assays, was investigated by direct sequencing of PCR fragments derived from the coding portion of the protein C gene. AG (8856) to A transition was noted in the patient which was not present in healthy controls. This mutation is predicted to cause the substitution of Ser for Gly 381, an evolutionari'y conserved residue in the substrate binding pocket of serine-proteases (Gly 216, chymotrypsin numbering). A computer model of the structure of the serine-protease domain indicates that the properties of the altered protein C molecule can be explained on the basis of steric hindrance between the substituted serine and the substrate arginine side chains.

Adult↗
PubMed1993

A molecular model of the serine protease domain of activated protein C: application to the study of missense mutations causing protein C deficiency.

A molecular model of the serine protease domain of protein C was constructed by standard comparative methods. Individual missense mutations were inserted into the model and plausible explanations for their interference with protein C structure/function were derived through consideration of location, steric effects and protein stability. A hydrophilic cluster of many Arg and Lys residues, found adjacent to the active site cleft, is proposed to be involved in thrombomodulin and/or protein S interactions. Analysis of comparative binding studies also suggested the presence of an extended substrate binding pocket in the model.

Amino Acid Sequence↗
PubMed1993

A novel dysfunctional protein C (protein C Padua 2) associated with a thrombotic tendency: substitution of Cys for Arg-1 results in a strongly reduced affinity for binding of Ca++.

A dysfunctional protein C (PC) molecule (Protein C Padua 2) was found in a 40-year-old man presenting with recurrent deep vein thrombosis/pulmonary embolism and a family history of thrombotic disease. The patient exhibited a normal PC antigen level, normal chromogenic activity (using Protac as PC activator) but markedly reduced coagulometric activity. After adsorption of patient plasma onto Al(OH)3, between 30% and 45% PC antigen/chromogenic activity but no coagulometric activity was detectable in the supernatant. The dysfunctional molecule exhibited reduced affinity for a Ca++ dependent anti-protein C monoclonal antibody as detected by specific ELISA assay. Immunoblotting experiments showed that PC Padua 2 had an increased MW (95 kD v 65 kD for normal PC). The lesion responsible was determined by PCR/direct sequencing to be a heterozygous CGT/TGT transition in exon 3 of the protein C gene resulting in the substitution of Arg by Cys at residue--1 in the pro-peptide leader sequence. The presence of a high MW PC was consistent with the fact that (part of) the propeptide (at least Cys-1) still was attached to the protein C molecule. This finding could also explain the strongly reduced affinity of PC Padua 2 for the Ca++ dependent anti-protein C monoclonals.

Adult↗
PubMed1993

Human gene mutations affecting RNA processing and translation.

Gene mutations affecting mRNA processing and translation are not common causes of human genetic disease. Their analysis has nevertheless provided important insights into the basic biochemical mechanisms underlying mRNA transcription and translation.

Base Sequence↗
PubMed1992

Sequence and specificity of a soluble lactose-binding lectin from Xenopus laevis skin.

A 16-kDa lactose-binding lectin comprises 5% or more of the soluble protein in Xenopus laevis skin. This lectin is mainly localized in the cytoplasm of granular gland cells. In response to stress, the lectin along with a variety of toxic and antibiotic peptides are released onto the skin surface by holocrine secretion. We have purified the lectin, sequenced tryptic peptides using tandem mass spectrometry and Edman degradation, and isolated full-length cDNA using a deduced oligonucleotide. Comparison of the cDNA and peptide sequences revealed expression of at least two isolectins, which differ in sequence at only two or three amino acids. Comparison of cDNA with complementary message by ribonuclease protection confirmed expression in approximately equal abundance of two nearly identical messages. The major soluble lactose-binding lectin expressed in Xenopus muscle is composed of these same isolectins, but at 100-fold lower levels. Similarities and distinctions in sequence and carbohydrate-binding specificity indicate that this lectin is a novel member of a family of soluble lactose-binding lectins expressed in a wide range of vertebrate tissues.

Amino Acid Sequence↗
PubMed1992

A comprehensive list of cloned human DNA sequences--1991 update.

An updated list of DNA sequences cloned from the human genome over the past year (1991) is presented. Intended as a guide to clone availability, this list includes published reports of cDNA, genomic and synthetic probes comprising both gene and pseudogene sequences.

DNA↗
PubMed1992

Prenatal exclusion of haemophilia A and carrier testing by direct detection of a disease lesion.

A novel mutation was detected in the Factor VIII gene of a sporadic case of severe haemophilia A. The lesion, a CGA-->TGA transition, converts Arg 795 to Term and adequately accounts for the severe phenotype observed. PCR/direct sequencing was used to confirm the carrier status in the mother. Exclusion of haemophilia A in an at-risk pregnancy was then achieved by demonstration of the absence of this lesion in fetal DNA from a chorionic villus sample. The mutation was also detectable by chemical cleavage of mismatch (CCM), which both confirmed the prenatal diagnosis and established the carrier status of the proband's sister. This example therefore serves to illustrate the potential of direct gene analysis in sporadic cases of haemophilia A and/or in families uninformative for known RFLPs.

Base Sequence↗
PubMed1992

Single-strand conformation polymorphism (SSCP) analysis of exon 11 of the CFTR gene reliably detects more than one third of non-delta F508 mutations in German cystic fibrosis patients.

In Central Europe, the delta F508 deletion accounts for approximately 75% of mutations in the cystic fibrosis transmembrane conductance regulator gene causing cystic fibrosis. The remainder comprise a large number of individually infrequent mutations whose detection requires a disproportionately large effort. However, a sizeable proportion of non-delta F508 mutations have been found to cluster within exon 11. We have taken advantage of this clustering to detect a total of five previously described point mutations present on 26/72 (36%) non-delta F508 chromosomes by polymerase chain reaction/direct sequencing of exon 11. These exon 11 mutations were then subjected to single-strand conformation polymorphism (SSCP) analysis, which was shown (i) to discriminate reliably between mutant and wildtype alleles and (ii) to generate reproducible mutation-specific band patterns. This analysis thus represents the first attempt to assess SSCP analysis retrospectively, and serves to illustrate the potential of this screening technique in diagnostic medicine.

Base Sequence↗
PubMed1992

Protein C deficiency and thromboembolism: recurrent mutation at Arg 306 in the protein C gene.

A CGA----TGA transition in the protein C gene, resulting in an Arg306----Term substitution, was detected in a Swedish kindred with thrombotic disease whose members exhibit plasma protein C activity/antigen levels consistent with type I protein C deficiency. Although an identical lesion has been reported previously in several Dutch families, RFLP typing indicated that the Dutch and Swedish mutations were unlikely to be identical by descent and probably arose by recurrent mutation.

Amino Acid Sequence↗
PubMed1992

Omission of exon 12 in cystic fibrosis transmembrane conductance regulator (CFTR) gene transcripts.

Cystic fibrosis transmembrane conductance regulator (CFTR) mRNA transcripts isolated from both expressing and "non-expressing" cell types of normal individuals exhibit differential splicing to a variable extent in a region encoding the putative nucleotide binding fold of the CFTR polypeptide. Sequence analysis of the aberrant fragments obtained after cDNA polymerase chain reaction amplification confirmed the in-frame joining of exons 11 and 13. The proportion of alternative splicing is reproducible and constant in a given individual. The omission of exon 12 in a significant proportion of transcripts supports the hypothesis that a minimal amount of correctly expressed CFTR is sufficient for the maintenance of a clinically normal phenotype.

Base Sequence↗