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At least 865 records · Page 48Linked to original sources
PubMed1988

The three-dimensional structure of Bacillus amyloliquefaciens subtilisin at 1.8 A and an analysis of the structural consequences of peroxide inactivation.

The three-dimensional structure of the subtilisin from Bacillus amyloliquefaciens (BAS) has been refined to 1.8 A using the amino acid sequence deduced from the DNA coding sequence. The structure is essentially the same as the previously reported structures of subtilisin BPN' (Wright, C.S., Alden, R.A., and Kraut, J. (1969) Nature 221, 235-242) and Novo (Drenth, J., Hol, W. G. J., Jansonius, J. N., and Koekoek, R. (1972) Eur. J. Biochem. 26, 177-181) determined in different crystal forms, at 2.5 and 2.8 A resolution, respectively. The largest differences in the three crystallographic models are seen in regions where the amino acid sequence used in the fit to the electron density maps of BPN' and Novo differs from the gene sequence of BAS (Wells, J. A., Ferrari, E., Henner, D. J., Estell, D. A., and Chen, E. Y. (1983) Nucleic Acids Res. 11, 7911-7925). The refined BAS model shows new features of cation binding, hydrogen bonding, and internal solvent structure. The refined BAS model has served as a basis for the analysis of stereochemical factors involved in the peroxide inactivation of the enzyme. Methionine 222, which is adjacent to the catalytic Ser221, is quantitatively oxidized to the sulfoxide by hydrogen peroxide as had been previously shown for the related Bacillus licheniformis enzyme (Stauffer, C. E., and Etson, D. (1969) J. Biol. Chem. 244, 5333-5338). In addition to this site of modification, we observe partial to full oxidation of two of the four remaining methionines. The oxidation of the methionines does not correlate well with their solvent accessibility calculated from the x-ray structure coordinates; in addition, only one of the two possible stereoisomers of methionine sulfoxide is formed. We also detect hydrogen peroxide-induced modification of the hydroxyl groups of two tyrosines. Modeling suggests that most of the observed effect of oxidation on the enzyme's catalytic efficiency can be attributed to unfavorable interactions at the oxyanion binding site between the sulfoxide group at 222 and the carbonyl oxygen of the scissile peptide bond of the bound substrate.

Bacillus↗
PubMed1986

The refined structure of vitamin D-dependent calcium-binding protein from bovine intestine. Molecular details, ion binding, and implications for the structure of other calcium-binding proteins.

The structure of bovine intestinal calcium-binding protein (ICaBP) has been determined crystallographically at a resolution of 2.3 A and refined by a least squares technique to an R factor of 17.8%. The refined structure includes all 600 non-hydrogen protein atoms, two bound calcium ions, and solvent consisting of one sulfate ion and 36 water molecules. The molecule consists of two helix-loop-helix calcium-binding domains known as EF hands, connected by a linker containing a single turn of helix. Helix-helix interactions are primarily hydrophobic, but also include a few strategic hydrogen bonds. Most of the hydrogen bonds, however, are found in the calcium-binding loops, where they occur both within a single loop and between the two. Examination of the hydrogen bonding patterns in the calcium-binding loops of ICaBP and the related protein, parvalbumin, reveals several conserved hydrogen bonds which are evidently important for loop stabilization. The primary and tertiary structural features which promote the formation of an EF hand were originally identified from the structure of parvalbumin. They are modified in light of the ICaBP structure and considered as they apply to other calcium-binding proteins. The C-terminal domain of ICaBP is a normal EF hand, with ion binding properties similar to those of the calmodulin hands, but the N-terminal domain is a variant hand whose calcium ligands are mostly peptide carbonyls. Relative to a normal EF hand, this domain exhibits a similar KD for calcium binding but a greatly reduced affinity for calcium analogs such as cadmium and the lanthanide series. Lanthanides in particular may be inappropriate models for calcium in this system.

Amino Acid Sequence↗
PubMedDate not supplied

[Stereochemical theory of the 3-dimensional structure of globular proteins. III. Prediction of the tertiary structure].

A prediction is made of the tertiary structure of parvalbumin, the variable part of the immunoglobulin molecule, carboxypeptidase and the trypsin inhibitor. The structures obtained theoretically coincide completely with the native ones. In the case of the trypsin inhibitor molecule, the theoretical sequence of disulfide bridge formation completely coincides with the experimental data. Elements of symmetry were found in highly helical intermediate structures of the four proteins studied. The theory developed can be successfully applied for assembling the quaternary protein structure. Proceeding from this theory the mechanisms of the increased rate of assembly of protein spatial structure in conditions in vivo as compared with their assembly in vitro are analysed.

Animals↗
PubMed2003

Structure-function relationship of reduced cytochrome c probed by complete solution structure determination in 30% acetonitrile/water solution.

The complete solution structure of ferrocytochrome c in 30% acetonitrile/70% water has been determined using high-field 1D and 2D (1)H NMR methods and deposited in the Protein Data Bank with codes 1LC1 and 1LC2. This is the first time a complete solution protein structure has been determined for a protein in nonaqueous media. Ferrocyt c retains a native protein secondary structure (five alpha-helices and two omega loops) in 30% acetonitrile. H18 and M80 residues are the axial heme ligands, as in aqueous solution. Residues believed to be axial heme ligands in the alkaline-like conformers of ferricyt c, specifically H33 and K72, are positioned close to the heme iron. The orientations of both heme propionates are markedly different in 30% acetonitrile/70% water. Comparative structural analysis of reduced cyt c in 30% acetonitrile/70% water solution with cyt c in different environments has given new insight into the cyt c folding mechanism, the electron transfer pathway, and cell apoptosis.

Acetonitriles↗
PubMed2003

A quantitative structure-antifungal activity relationship study of oxygenated aromatic essential oil compounds using data structuring and PLS regression analysis.

Twenty two oxygenated aromatic essential oil compounds were chosen for the study of the antifungal activity against two wood-decaying fungi, the white-rot Trametes versicolor, which mainly metabolizes lignin, and the brown-rot Coniophoha puteana, which digests cellulose in plant cell walls. Minimal inhibitory concentrations (MICs) were determined by the agar dilution method, using dimethyl sulfoxide (DMSO) as the solvent for the selected compounds and potato-dextrose agar (PDA) as the growth medium for both fungi. The MICs were then used to generate a tree structure, which represents the structuring of the essential oil compounds by the nature and position of the substituents in their aromatic rings, and as dependent variables (log(1/MIC)) in the QSAR analysis. Data structuring proved that a relationship between the molecular structures of the essential oil compounds and their antifungal activity exists, and the hypotheses derived therefrom were complemented by performing a QSAR analysis using the partial least squares (PLS) method. Statistically significant PLS models were obtained with the 1-octanol-water partition coefficient (C log P), the energy of the highest occupied molecular orbital (E(HOMO)), and the number of hydrogen-bond donor atoms in the molecules of the compounds studied (Donor) for T. versicolor and with C log P and the fractional negative surface area (FNSA1) for C. puteana.

Aldehydes↗
PubMed2004

Effect of glycine substitutions on alpha5(IV) chain structure and structure-phenotype correlations in Alport syndrome.

The phenotype variety caused by glycine substitutions in alpha5(IV) chain in X-linked Alport syndrome (XLAS) prompted the complexity of structure changes of alpha5(IV) chain that was little to know now. In this study, we expressed a domain of alpha5(IV) chain containing different glycine substitutions (G1015V and G1030S, respectively) which were revealed in two XLAS pedigrees with different phenotype severities and the corresponding domain of a control in Escherichia coli. The recombinant proteins were characterized by immunoblot and mass spectrometry and analyzed the secondary structure by using circular dichroism (CD) spectroscopy. CD analysis showed that the recombinant protein containing G1015V mutation identified in the pedigree of juvenile-onset XLAS exhibited 12.9% alpha-helix that was not found in the control recombinant protein. The spectrum of the recombinant protein containing G1030S mutation identified in the pedigree of adult-onset XLAS was slightly different from that of the control, that is, mostly with the random coil and the beta-sheet, while without alpha-helix. These results demonstrated that two kinds of glycine substitutions, although in the same domain of alpha5(IV) chain, displayed the distinctly different secondary structures. The changes of the secondary structure could explain the phenotypic diversities of XLAS, which would be hardly understood solely by analyzing genomic DNA or mRNA of alpha5(IV) chain.

Adolescent↗
PubMed2005

Structural bases of feed-back control of arginine biosynthesis, revealed by the structures of two hexameric N-acetylglutamate kinases, from Thermotoga maritima and Pseudomonas aeruginosa.

N-Acetylglutamate kinase (NAGK) catalyses the second step in the route of arginine biosynthesis. In many organisms this enzyme is inhibited by the final product of the route, arginine, and thus plays a central regulatory role. In addition, in photosynthetic organisms NAGK is the target of the nitrogen-signalling protein PII. The 3-D structure of homodimeric, arginine-insensitive, Escherichia coli NAGK, clarified substrate binding and catalysis but shed no light on arginine inhibition of NAGK. We now shed light on arginine inhibition by determining the crystal structures, at 2.75 A and 2.95 A resolution, of arginine-complexed Thermotoga maritima and arginine-free Pseudomonas aeruginosa NAGKs, respectively. Both enzymes are highly similar ring-like hexamers having a central orifice of approximately 30 A diameter. They are formed by linking three E.coli NAGK-like homodimers through the interlacing of an N-terminal mobile kinked alpha-helix, which is absent from E.coli NAGK. Arginine is bound in each subunit of T.maritima NAGK, flanking the interdimeric junction, in a site formed between the N helix and the C lobe of the subunit. This site is also present, in variable conformations, in P.aeruginosa NAGK, but is missing from E.coli NAGK. Arginine, by gluing the C lobe of each subunit to the inter-dimeric junction, may stabilize an enlarged active centre conformation, hampering catalysis. Acetylglutamate counters arginine inhibition by promoting active centre closure. The hexameric architecture justifies the observed sigmoidal arginine inhibition kinetics with a high Hill coefficient (N approximately 4), and appears essential for arginine inhibition and for NAGK-PII complex formation, since this complex may involve binding of NAGK and PII with their 3-fold axes aligned. The NAGK structures allow identification of diagnostic sequence signatures for arginine inhibition. These signatures are found also in the homologous arginine-inhibited enzyme NAG synthase. The findings on NAGK shed light on the structure, function and arginine inhibition of this synthase, for which a hexameric model is constructed.

Amino Acid Sequence↗
PubMed2006

Crystal structure of nicotinic acid mononucleotide adenylyltransferase from Staphyloccocus aureus: structural basis for NaAD interaction in functional dimer.

Bacterial nicotinic acid mononucleotide adenylyltransferase (NaMNAT; EC 2.7.7.18) encoded by the nadD gene, is essential for cell survival and is thus an attractive target for developing new antibacterial agents. The NaMNAT catalyzes the transfer of an adenylyl group of ATP to nicotinic acid mononucleotide (NaMN) to form nicotinic acid dinucleotide (NaAD). Two independently derived, high-resolution structures of Staphylococcus aureus NaMNAT-NaAD complexes establish the conserved features of the core dinucleotide-binding fold with other adenylyltransferases from bacteria to human despite a limited sequence conservation. The crystal structures reveal that the nicotinate carboxylates of NaAD are recognized by interaction with the main-chain amides of Thr85 and Tyr117, a positive helix dipole and two bridged-water molecules. Unlike other bacterial adenylyltransferases, where a partially conserved histidine residue interacts with the nicotinate ring, the Leu44 side-chain interacts with the nicotinate ring by van der Waals contact. Importantly, the S. aureus NaMNAT represents a distinct adenylyltransferase subfamily identifiable in part by common features of dimerization and substrate recognition in the loop connecting beta5 to beta6 (residues 132-146) and the additional beta6 strand. The unique beta6 strand helps orient the residues in the loop connecting beta5 to beta6 for substrate/product recognition and allows the beta7 strand structural flexibility to make key dimer interface interactions. Taken together, these structural results provide a molecular basis for understanding the coupled activity and recognition specificity for S. aureus NaMNAT and for rational design of selective inhibitors.

Amino Acid Sequence↗
PubMed2005

Conservation of the capsid structure in tailed dsDNA bacteriophages: the pseudoatomic structure of phi29.

Bacteriophage phi29 is one of the smallest and simplest known dsDNA phages, making it amenable to structural investigations. The three-dimensional structure of a fiberless, isometric variant has been determined to 7.9 A resolution by cryo-electron microscopy (cryo-EM), allowing the identification of alpha helices and beta sheets. Their arrangement indicates that the folds of the phi29 and bacteriophage HK97 capsid proteins are similar except for an additional immunoglobulin-like domain of the phi29 protein. An atomic model that incorporates these two domains fits well into the cryo-EM density of the T = 3, fiberless isometric phi29 particle, and cryo-EM structures of fibered isometric and fiberless prolate prohead phi29 particles at resolutions of 8.7 A and 12.7 A, respectively. Thus, phi29 joins the growing number of phages that utilize the HK97 capsid structure, suggesting that this protein fold may be as prevalent in capsids of dsDNA phages as the jelly roll fold is in eukaryotic viruses.

Bacillus Phages↗
PubMed2002

Crystal structure of decameric fructose-6-phosphate aldolase from Escherichia coli reveals inter-subunit helix swapping as a structural basis for assembly differences in the transaldolase family.

Fructose-6-phosphate aldolase from Escherichia coli is a member of a small enzyme subfamily (MipB/TalC family) that belongs to the class I aldolases. The three-dimensional structure of this enzyme has been determined at 1.93 A resolution by single isomorphous replacement and tenfold non-crystallographic symmetry averaging and refined to an R-factor of 19.9% (R(free) 21.3%). The subunit folds into an alpha/beta barrel, with the catalytic lysine residue on barrel strand beta 4. It is very similar in overall structure to that of bacterial and mammalian transaldolases, although more compact due to extensive deletions of additional secondary structural elements. The enzyme forms a decamer of identical subunits with point group symmetry 52. Five subunits are arranged as a pentamer, and two ring-like pentamers pack like a doughnut to form the decamer. A major interaction within the pentamer is through the C-terminal helix from one monomer, which runs across the active site of the neighbouring subunit. In classical transaldolases, this helix folds back and covers the active site of the same subunit and is involved in dimer formation. The inter-subunit helix swapping appears to be a major determinant for the formation of pentamers rather than dimers while at the same time preserving importing interactions of this helix with the active site of the enzyme. The active site lysine residue is covalently modified, by forming a carbinolamine with glyceraldehyde from the crystallisation mixture. The catalytic machinery is very similar to that of transaldolase, which together with the overall structural similarity suggests that enzymes of the MipB/TALC subfamily are evolutionary related to the transaldolase family.

Aldehyde-Lyases↗
PubMed2000

Determination of the structure of Escherichia coli glyoxalase I suggests a structural basis for differential metal activation.

The metalloenzyme glyoxalase I (GlxI) converts the nonenzymatically produced hemimercaptal of cytotoxic methylglyoxal and glutathione to nontoxic S-D-lactoylglutathione. Human GlxI, for which the structure is known, is active in the presence of Zn(2+). Unexpectedly, the Escherichia coli enzyme is inactive in the presence of Zn(2+) and is maximally active with Ni(2+). To understand this difference in metal activation and also to obtain a representative of the bacterial enzymes, the structure of E. coli Ni(2+)-GlxI has been determined. Structures have also been determined for the apo enzyme as well as complexes with Co(2+), Cd(2+), and Zn(2+). It is found that each of the protein-metal complexes that is catalytically active has octahedral geometry. This includes the complexes of the E. coli enzyme with Ni(2+), Co(2+), and Cd(2+), as well as the structures reported for the human Zn(2+) enzyme. Conversely, the complex of the E. coli enzyme with Zn(2+) has trigonal bipyramidal coordination and is inactive. This mode of coordination includes four protein ligands plus a single water molecule. In contrast, the coordination in the active forms of the enzyme includes two water molecules bound to the metal ion, suggesting that this may be a key feature of the catalytic mechanism. A comparison of the human and E. coli enzymes suggests that there are differences between the active sites that might be exploited for therapeutic use.

Bacterial Proteins↗
PubMed2002

NMR structure of a minimum activity domain of human parathyroid peptide hormone: structural origin of receptor activation.

Parathyroid hormone (PTH) which increases osteoblast numbers and bone formation by activating bone-lining cells to osteoblasts plays an important role in calcium and phosphate homeostasis and bone remodeling by activating PTH receptors. To determine the structural origin of a minimum activity domain of hPTH, we initiated a detailed structural determination of the hPTH(H14) in aqueous solution using NMR spectroscopy. Circular dichroism and NMR data demonstrated that hPTH(H14) maintains a typical helical conformation in both membrane-mimicking environments and 30% TFE solution. The solution structure clearly showed that the residues from Ser(3) to Leu(11) of hPTH(H14) formed a stable helical structure, especially having charged side-chains oriented in opposite directions relative to one another for optimum interaction with the receptor molecule.

Amino Acid Sequence↗
PubMed2005

Three-dimensional structure of human monoamine oxidase A (MAO A): relation to the structures of rat MAO A and human MAO B.

The three-dimensional structure of recombinant human monoamine oxidase A (hMAO A) as its clorgyline-inhibited adduct is described. Although the chain-fold of hMAO A is similar to that of rat MAO A and human MAO B (hMAO B), hMAO A is unique in that it crystallizes as a monomer and exhibits the solution hydrodynamic behavior of a monomeric form rather than the dimeric form of hMAO B and rat MAO A. hMAO A's active site consists of a single hydrophobic cavity of approximately 550 A3, which is smaller than that determined from the structure of deprenyl-inhibited hMAO B (approximately 700 A3) but larger than that of rat MAO A (approximately 450 A3). An important component of the active site structure of hMAO A is the loop conformation of residues 210-216, which differs from that of hMAO B and rat MAO A. The origin of this structural alteration is suggested to result from long-range interactions in the monomeric form of the enzyme. In addition to serving as a basis for the development of hMAO A specific inhibitors, these data support the proposal that hMAO A involves a change from the dimeric to the monomeric form through a Glu-151 --> Lys mutation that is specific of hMAO A [Andrès, A. M., Soldevila, M., Navarro, A., Kidd, K. K., Oliva, B. & Bertranpetit, J. (2004) Hum. Genet. 115, 377-386]. These considerations put into question the use of MAO A from nonhuman sources in drug development for use in humans.

Animals↗
PubMed2004

Crystal structure of the phosphorolytic exoribonuclease RNase PH from Bacillus subtilis and implications for its quaternary structure and tRNA binding.

RNase PH is a member of the family of phosphorolytic 3' --> 5' exoribonucleases that also includes polynucleotide phosphorylase (PNPase). RNase PH is involved in the maturation of tRNA precursors and especially important for removal of nucleotide residues near the CCA acceptor end of the mature tRNAs. Wild-type and triple mutant R68Q-R73Q-R76Q RNase PH from Bacillus subtilis have been crystallized and the structures determined by X-ray diffraction to medium resolution. Wild-type and triple mutant RNase PH crystallize as a hexamer and dimer, respectively. The structures contain a rare left-handed beta alpha beta-motif in the N-terminal portion of the protein. This motif has also been identified in other enzymes involved in RNA metabolism. The RNase PH structure and active site can, despite low sequence similarity, be overlayed with the N-terminal core of the structure and active site of Streptomyces antibioticus PNPase. The surface of the RNase PH dimer fit the shape of a tRNA molecule.

Amino Acid Sequence↗
PubMed2000

Solution structure of a peptide model of a region important for the folding of alpha-lactalbumin provides evidence for the formation of nonnative structure in the denatured state.

Elucidating the properties of the denatured state of proteins under conditions relevant for their folding is a key factor in understanding the folding process. We show that a peptide corresponding to residues 111-120 of human alpha-lactalbumin has a pronounced propensity to adopt nonnative structure in aqueous solution. Two-dimensional NMR provides evidence for a structured, nonnative conformation in fast exchange with a random coil ensemble. A total of 78 Rotating Frame Overhauser Effects (ROEs) were used to calculate the conformation of the structured population. A nonnative cluster of hydrophobic residues involving the side chains of K114, W118, Ll119, and A120 is observed, which helps to stabilize a turn-like conformation in the vicinity of residues 115-118. The structure in 30% (vol/vol) TFE was also calculated. Interestingly, the addition of TFE did not simply amplify the population of the structured conformer observed in H2O, but instead induced a new conformation. The implications for the folding of the intact protein are discussed. We also discuss the implications of this study for the relevance of the use of mixed TFE/H2O solvent systems to study isolated peptides.

Circular Dichroism↗
PubMed1997

Design of specific structures using alpha,beta-dehydro-phenylalanine residues: synthesis, crystal structure, and molecular conformation of Boc-L-Val-delta Phe-delta Phe-L-Val-delta Phe-delta Phe-L-Val-OCH3, a 3(10)-helical heptapeptide.

The peptide design using alpha,beta-dehydro-residues has wide applications. To design an extensive 3(10)-helical conformation, a heptapeptide Boc-L-Val-delta Phe-delta Phe-L-Val-delta Phe-delta Phe-L-Val-OCH3, with a repeat of two consecutive delta Phe residues has been synthesized using an azlactone method in solution phase. This is the first design using a repeat of two consecutive delta Phe residues. It is observed that the delta Phe in a sequence of two consecutive delta Phe residues, adopts only one set of phi, psi values, i.e., +/- 60 degrees, +/- 30 degrees, thus making it a specific design tool. The peptide crystallized from its solution in a methanol-water mixture in the space group P2(1) with a = 10.159(5)A, b = 20.057(2)A, c = 14.448(3)A, beta = 99.41(2)degrees, V = 2904(2)A3. The structure has been determined by direct methods and refined to an R value of 0.048 for 5404 observed [I > or = 3 sigma(I)] reflections. The structure consists of a heptapeptide Boc-L-Val-delta Phe-delta Phe-L-Val-delta Phe-delta Phe-L-Val-OCH3 and a solvent methanol molecule in the asymmetric unit. All peptide units in the structure are trans. As a result of six overlapping type III beta-turns formed involving seven residues and five intramolecular 4-->1 hydrogen bonds, the peptide adopts a right-handed 3(10)-helical conformation with more than two complete helical turns. It is noteworthy that starting from the Boc group to the C-terminal residue of Val, the 3(10)-helical structure is maintained well. The carbonyl oxygen atom of the Boc group is the first acceptor whereas the carbonyl oxygen atom of Val4 is the last acceptor in the helical structure of the peptide. The side chains of four delta Phe residues in this helical arrangement exist in a slightly staggered arrangement. The solvent methanol molecule interacts through its hydroxyl group and forms two intermolecular hydrogen bonds, one as a donor with a C-terminal CO group of delta Phe6 and second as an acceptor with the NH group of delta Phe2 from the N-terminal region of the peptide. Thus the solvent molecule plays a significant role in promoting a head-to-tail packing of 3(10)-helices of the peptide. There are no lateral hydrogen bonds between the helices, but there exist several van der Waals interactions involving the hydrophobic side chains of peptide molecules.

Crystallography, X-Ray↗
PubMed2000

Self-penetration--a structural compromise between single networks and interpenetration: magnetic properties and crystal structures of

The three-dimensional coordination polymers [Mn(dca)2(H2O)] (1) and [M(dca)(tcm)], M =Co (2), Ni (3), Cu (4), dca =dicyanamide, N(CN)2-, tcm = tricyanomethanide, C(CN)3-, have isomorphous structures. In 1 half the dca ligands coordinate directly (through all three nitrogen atoms) to three Mn atoms (all metal atoms are six-coordinate), while the other half coordinate to two Mn atoms (through the nitrile nitrogens) and hydrogen bond to water molecules coordinated to a third Mn atom (through the amide nitrogen). This dca. H2O structural moiety is disordered over a mirror plane, and is replaced by the structurally equivalent tcm ligand in compounds 2-4. The resulting structures display a new self-penetrating 3,6-connected (2:1) network topology that can be related to, but is different from, the rutile net. The self-penetrating [M(dca)(tcm)] network can be viewed as a structural compromise between the two interpenetrating rutile-like networks of [M(tcm)2] and the single rutile-like network of alpha-[M(dca)2]. The temperature and field dependence of the DC and AC magnetic susceptibilities and magnetisations has been measured for complexes 1-4. Compounds 1-3 exhibit long-range magnetic order with critical temperatures of 6.3 K for 1, 3.5 K for 2 and 8.0 K for 3. The Cu11 compound 4 does not order and is essentially a paramagnet. Hysteresis measurements of coercive field and remnant magnetisation show that 1, 2 and 3 are soft magnets, 1 being a canted-spin antiferromagnet (weak ferromagnet), while 2 and 3 are ferromagnets that display some unusual features in their high-field magnetisation isotherms in comparison to their related alpha-[M(dca)2] phases.

Journal Article↗
PubMed1987

A variant of type II von Willebrand disease with an abnormal triplet structure and discordant effects of protease inhibitors on plasma and platelet von Willebrand factor structure.

We have characterized the plasma and platelet von Willebrand factor (vWf) multimeric structure of a patient with von Willebrand disease (vWd) as having a long bleeding time, no aggregation of her platelet-rich plasma (PRP) to ristocetin, and very low plasma and platelet von Willebrand antigen (vWf Ag) and vWf activity. The abnormalities of the plasma and platelet vWf have not been previously described. In particular, the patient's plasma and platelet vWf lacked the intermediate and largest vWf multimers and the slowest migrating minor band (band 1) of the triplet was markedly diminished compared to the major band (band 2) and the fastest migrating band of the triplet (band 3). A similar multimeric structure was seen in the platelet vWf. Collection of the patient's blood in protease inhibitors prior to the analysis of the platelet and plasma vWf structure revealed that the plasma vWf multimeric structure did not change, while the patient's platelet vWf showed a marked change with the appearance of the intermediate and large multimers and almost total disappearance of the abnormal multimeric structure. Direct comparison of this patient's plasma with previously reported cases of type IIA, IIC, and IID revealed marked differences in their multimeric organization compared to our patient. Employing the presently accepted convention, we have designated this variant type of vWd type IIG.

Blood Platelets↗