Flow cytometric studies of the D antigen of various Rh phenotypes with particular reference to Du and Del

Flow cytometric analysis was performed on red cells (RBCs) to compare the antigen activity of various Rh phenotypes, including the rare variants Del and Du (both high-grade and low-grade), whose genotypes were confirmed or presumed by the family study. This appears to be the first report that the Del phenotype is due to the inhibitory effect of Cde. This study also compares the quantity of the D antigen in different phenotypes, whose genotypes comprise the same Du gene (cDuE) transmitted in a family. RBCs were stained by the indirect immunofluorescence method using IgG anti-D purified through a protein-A affinity column. The mean fluorescence intensity obtained for each genotype representing the activity of the D antigen decreased in the following order (percentages show relative fluorescence intensity taking cDE/cDE control as 100% and Cde/cde as 0%): CDe/cDE, 76 percent; CDe/cde, 73 percent; cDE/Cde, 70 percent; cDE/cDuE, 68 percent; CDe/Cde (high-grade Du), 59 percent; cDuE/cde (low-grade Du), 6 percent; and cDuE/Cde (Del), 3 to 4 percent.

Localization of the coagulation factor XIII B subunit gene (F13B) to chromosome bands 1q31-32.1 and restriction fragment length polymorphism at the locus

In situ hybridization of tritiated cDNA probes for the gene for the B subunit of coagulation factor XIII localized the F13B locus to bands q31-q32.1 on human chromosome 1 and perhaps more precisely to sub-bands 1q31.2 or 1q31.3. Restriction fragment length polymorphisms (RFLPs) were detected with BglII, EcoRI and XbaI. Because the RFLPs detected with each of the three enzymes were concordant in every individual studied and since each showed a similar size difference, it was concluded that the RFLPs probably result from an insertion or deletion of length approximately 0.37-0.4 kb.

Characterization of the gene for the a subunit of human factor XIII (plasma transglutaminase), a blood coagulation factor

Factor XIII (plasma transglutaminase, fibrin stabilizing factor) is a glycoprotein that circulates in blood as a tetramer (a2b2) consisting of two a and two b subunits. The primary structures of the a and b subunits of human factor XIII have been reported by a combination of cDNA cloning and amino acid sequence analysis. To establish the gene structure of the a subunit for factor XIII, several human genomic libraries were screened by using the cDNA encoding the a subunit as a probe. Among approximately equal to 5 x 10(7) recombinant phage, 121 have been shown to contain an insert encoding a portion of the a subunit. Twenty-five unique clones were then characterized by restriction mapping, Southern blotting, and DNA sequencing. Overlapping clones encoding the a subunit of factor XIII span greater than 160 kilobases. The gene was found to contain 15 exons separated by 14 introns. All the sequences of the introns at the intron-exon boundaries were GT-AG, which are the same as those found in other eukaryotic genes. DNA sequence analysis revealed that the activation peptide released by thrombin, the active site cysteine region, the two putative calcium-binding regions, and the thrombin cleavage site leading to inactivation are encoded by separate exons. This suggests that the introns may separate the a subunit into functional and structural domains. A comparison of the amino acid sequence deduced from the genomic DNA sequence with those deduced from cDNA or determined by amino acid sequence analysis of the plasma and placental proteins revealed apparent amino acid polymorphisms in six positions of the polypeptide chain of the a subunit.

Localization of the coagulation factor XIII A subunit gene (F13A) to chromosome bands 6p24----p25

Electrophoretic studies of the genetic variation of the A subunit of coagulation factor XIII (F13A) have shown that the A subunits expressed in placenta and in the circulation are the products of the same gene locus. In situ hybridization studies with a cDNA fragment encoding the amino terminal region of the A subunit have localized the gene to bands p24----p25 on chromosome 6. This confirms previous studies that showed linkage between F13A and the major histocompatibility complex.

Primary structure of human coagulation factor XIII

The complete primary structures of the a and b subunits of human factor XIII were determined by a combination of cDNA cloning and amino acid sequencing. The a subunit is composed of 731 amino acids including an activation peptide (37 amino acids), an active site (-Tyr-Gly-Gln-Cys-Glu-), a putative calcium binding site(s), and a thrombin-inactivation site. The functional regions of the a subunit appear to be located in separate exons of its gene. The b subunit consists of 641 amino acids including ten tandem repeats that are homologous with those in at least 13 other proteins. Each GP-I structure in the b subunit is probably encoded by a separate exon.

Cloning of cDNAs coding for the heavy chain region and connecting region of human factor V, a blood coagulation factor with four types of internal repeats

Human factor V is a high molecular weight plasma glycoprotein that participates as a cofactor in the conversion of prothrombin to thrombin by factor Xa. Prior to its participation in the coagulation cascade, factor V is converted to factor Va by thrombin generating a heavy chain and a light chain, and these two chains are held together by calcium ions. A connecting region originally located between the heavy and light chains is liberated during the activation reaction. In a previous study, a cDNA of 2970 nucleotides that codes for the carboxyl-terminal 938 amino acids of factor V was isolated and characterized from a Hep G2 cDNA library [Kane, W. H., & Davie, E. W. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 6800-6804]. This cDNA has been used to obtain additional clones from Hep G2 and human liver cDNA libraries. Furthermore, a Hep G2 cDNA library prepared with an oligonucleotide from the 5' end of these cDNAs was screened to obtain overlapping cDNA clones that code for the amino-terminal region of the molecule. The composite sequence of these clones spans 6911 nucleotides and is consistent with the size of the factor V message present in Hep G2 cells (approximately 7 kilobases). The cDNA codes for a leader sequence of 28 amino acids and a mature protein of 2196 amino acids. The amino acid sequence predicted from the cDNA was in complete agreement with 139 amino acid residues that were identified by Edman degradation of cyanogen bromide peptides isolated from the heavy chain region and connecting region of plasma factor V.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino acid sequence of the a subunit of human factor XIII

Factor XIII is a plasma protein that plays an important role in the final stages of blood coagulation and fibrinolysis. The complete amino acid sequence of the a subunit of human factor XIII was determined by a combination of cDNA cloning and amino acid sequence analysis. A lambda gtll cDNA library prepared from human placenta mRNA was screened with an affinity-purified antibody against the a subunit of human factor XIII and then with a synthetic oligonucleotide probe that coded for a portion of the amino acid sequence present in the activation peptide of the a subunit. Six positive clones were identified and shown to code for the a subunit of factor XIII by DNA sequence analysis. A total of 3831 base pairs was determined by sequencing six overlapping cDNA clones. This DNA sequence contains a 5' noncoding region or a region coding for a portion of a pro-piece or leader sequence, the mature protein (731 amino acids), a stop codon (TGA), a 3' noncoding region (1535 nucleotides), and a poly(A) tail (10 nucleotides). When the a subunit of human factor XIII was digested with cyanogen bromide, 11 peptides were isolated by gel filtration and reverse-phase HPLC. Amino acid sequence analyses of these peptides were performed with an automated sequenator, and 363 amino acid residues were identified. These amino acid sequences were in complete agreement with those predicted from the cDNA. The a subunit of factor XIII contained the active site sequence of Tyr-Gly-Gln-Cys-Trp, which is identical with that of tissue transglutaminase.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino acid sequence of the b subunit of human factor XIII, a protein composed of ten repetitive segments

Factor XIII is a plasma protein that participates in the final stages of blood coagulation. The complete amino acid sequence of the b subunit of human factor XIII was determined by a combination of cDNA cloning and amino acid sequence analysis. A lambda gt11 cDNA library prepared from human liver mRNA was screened with an affinity-purified antibody against the b subunit of human factor XIII. Nine positive clones were isolated from 2 X 10(6) phage and plaque-purified. The largest cDNA insert was sequenced and shown to contain 2180 base pairs coding for a portion of the leader sequence (19 amino acids), the mature protein (641 amino acids), a stop codon (TGA), a 3' noncoding region (187 nucleotides), and a poly(A) tail. When the b subunit of human factor XIII was digested with cyanogen bromide, nine peptides were isolated by gel filtration and reverse-phase high-performance liquid chromatography. Amino acid sequence analyses of these peptides were performed with an automated sequenator, and 299 amino acid residues were identified. These amino acid sequences were in complete agreement with the amino acid sequence predicted from the cDNA. The b subunit of factor XIII contained 10 repetitive homologous segments, each composed of about 60 amino acids and 4 half-cystine residues. Each of these repeated segments is a member of a family of repeats present in human beta 2-glycoprotein I, complement factor B, and haptoglobin alpha 1 chain. Three potential Asn-linked carbohydrate attachment sites were also identified in the b subunit of factor XIII.

Localization of the binding site of tissue-type plasminogen activator to fibrin

Functionally active A and B chains were separated from a two-chain form of recombinant tissue-type plasminogen activator after mild reduction and alkylation. The A chain was found to be responsible for the binding to lysine-Sepharose or fibrin and the B chain contained the catalytic activity of tissue-type plasminogen activator. An extensive reduction of two-chain tissue-type plasminogen activator, however, destroyed both the binding and catalytic activities. A thermolytic fragment, Fr. 1, of tissue-type plasminogen activator that contained a growth factor and two kringle segments retained its lysine binding activity. Additional thermolytic cleavages in the kringle-2 segment of Fr. 1 caused a total loss of the binding activity. These results indicated that the binding site of tissue-type plasminogen activator to fibrin was located in the kringle-2 segment.

The initiation of fibrinolysis in alpha 2-plasmin inhibitor deficient plasma. Role of fibrin

Plasmin activity and fibrin degradation products (FDP) are found in alpha 2-plasmin inhibitor (alpha 2-PI) deficient plasma only when clotted, but are not found when the plasma is not clotted. To determine whether fibrin itself could initiate fibrinolysis without activating coagulation enzymes, fibrin monomers were prepared and added to alpha 2-PI deficient plasma. The addition of fibrin monomers resulted in the generation of plasmin activity, a marked increase in FDP concentration, and the release of 125I from 125I-labeled fibrin monomers. Replenishment of the deficient plasma with purified alpha 2-PI abolished the effects of fibrin monomers on the initiation of fibrinolysis. Neither development of plasmin activity, increase of FDP, nor release of 125I was observed. These findings indicate that fibrinolysis can be induced by fibrin itself without activation of coagulation cascade and the induction of fibrinolysis is efficiently blocked by alpha 2-PI.

The activation of pro-urokinase by plasma kallikrein and its inactivation by thrombin

Plasma kallikrein was found to be a good activator of pro-urokinase, the inactive zymogen form of urokinase. The complete activation of pro-urokinase by plasma kallikrein was obtained in 2 h with an enzyme/substrate weight ratio of 1/30. The rate of activation of pro-urokinase by plasma kallikrein was comparable to that catalyzed by plasmin and trypsin. The rate of activation of pro-urokinase by factor XIIa was approximately one-seventh of that by plasma kallikrein. The activation of the zymogen was due to the cleavage of a single internal peptide bond, resulting in the conversion of a single chain pro-urokinase (Mr = 55,000) into two-chain urokinase (Mr = 33,000 and 22,000), and these two chains were linked by a disulfide bond(s). These results indicate an important role of plasma kallikrein for the activation of pro-urokinase in the factor XII-dependent intrinsic pathway of fibrinolysis. Thrombin also converted pro-urokinase to a two-chain form that was not activatable by plasmin, plasma kallikrein, and factor XIIa. Thrombin specifically cleaved the Arg 156-Phe 157 bond which is located 2 residues prior to the activation site of Lys 158-Ile 159.

Proteolytic activation of tissue plasminogen activator by plasma and tissue enzymes

Tissue kallikrein and factor Xa were found to activate tissue plasminogen activator (t-PA) at a rate comparable with that of plasmin. During the activation reaction, the single-chain molecule was converted into a two-chain form. A slight t-PA activating activity was also found in plasma kallikrein. Other activated coagulation factors, factor XIIa, factor XIa, factor IXa, factor VIIa, thrombin and activated protein C had no effect on t-PA activation. t-PA was also activated by a tissue kallikrein-like enzyme that was isolated from the culture medium of melanoma cells. These results indicate that tissue kallikrein and factor Xa may participate in the extrinsic pathway of human fibrinolysis.

Histidine-rich glycoprotein and alpha 2-plasmin inhibitor in inhibition of plasminogen binding to fibrin

The plasma proteins alpha 2-plasmin inhibitor and histidine-rich glycoprotein were compared directly with respect to their effectiveness in inhibiting the binding of plasminogen to fibrin under the same experimental conditions. At their physiological concentrations, the presence of alpha 2-plasmin inhibitor more markedly decreased the binding of plasminogen to fibrin than histidine-rich glycoprotein. Significance of these findings in inhibition of fibrinolysis is discussed.

Fibrin-associated plasminogen activation in alpha 2-plasmin inhibitor deficiency

The clot formed from the plasma of a patient with congenital deficiency of alpha 2-plasmin inhibitor underwent a spontaneous extensive fibrinolysis. Radiolabeled fibrinogen was added to the plasma before clotting, and the whole process of the fibrinolysis was followed by measuring the release of radiolabels. Plasminogen activation was also followed by measuring the amidolytic activity that developed. There was an initial latent period, followed by an exponential increase of fibrinolytic activity. During the latent period, there was little or no release of radiolabels and no development of amidolytic activity. During the latent period, the clot was washed thoroughly to remove unbound proteins from fibrin and was incubated in buffered saline. The washed clot still underwent fibrinolysis, similar to the original plasma clot, suggesting that the plasminogen/plasminogen activators bound to fibrin during the initial latent period are responsible for fibrinolysis. The amount of plasminogen bound to fibrin during the latent period was close to the amount of plasminogen activated during the whole process of fibrinolysis. When the amount of plasminogen bound to fibrin was decreased by epsilon aminocaproic acid, the extent of fibrinolysis was decreased in parallel with the decrease of the amount of the bound plasminogen. This suggests that the amount of plasminogen bound to fibrin is one of the determinants of the rate of the fibrinolytic process.

Factor XIII-mediated cross-linking of NH2-terminal peptide of alpha 2-plasmin inhibitor to fibrin

The NH2-terminal 12-residue peptide of alpha 2-plasmin inhibitor, Asn-Gln-Glu-Gln-Val-Ser-Pro-Leu-Thr-Gly-Leu-Lys-NH2 . AcOH, was found to be a good substrate for plasma transglutaminase (activated blood coagulation factor XIII) and rapidly incorporated into fibrin by the enzyme. A high concentration of the peptide inhibited the enzyme-mediated cross-linking of alpha 2-plasmin inhibitor to fibrin probably by competing with the inhibitor for the same site of fibrin alpha-chain.