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At least 919 records · Page 51Linked to original sources
PubMed1999

The TRA-1A sex determination protein of C. elegans regulates sexually dimorphic cell deaths by repressing the egl-1 cell death activator gene.

The hermaphrodite-specific neurons (HSNs) of the nematode Caenorhabditis elegans are generated embryonically in both hermaphrodites and males but undergo programmed cell death in males. The gene egl-1 encodes a BH3-containing cell death activator that is required for programmed cell death in C. elegans. Gain-of-function (gf) mutations in egl-1 cause the inappropriate programmed cell death of the HSNs in hermaphrodites. These mutations lie 5.6 kb downstream of the egl-1 transcription unit and disrupt the binding of the TRA-1A zinc finger protein, the terminal global regulator of somatic sexual fate. This disruption results in the activation of the egl-1 gene in the HSNs not only in males but also in hermaphrodites. Our findings suggest that in hermaphrodites TRA-1A represses egl-1 transcription in the HSNs to prevent these neurons from undergoing programmed cell death.

Animals↗
PubMed1991

Control of the sperm-oocyte switch in Caenorhabditis elegans hermaphrodites by the fem-3 3' untranslated region.

In the Caenorhabditis elegans hermaphrodite germ line, sperm and then oocytes are made from a common pool of germ-cell precursors. The decision to differentiate as a sperm or an oocyte is regulated by the sex-determining gene, fem-3. Expression of fem-3 in the hermaphrodite germ line directs spermatogenesis and must be negatively regulated to allow the switch to oogenesis. In adult hermaphrodites (which are producing oocytes), most fem-3 RNA is found in the germ line, consistent with both the requirement for fem-3 in hermaphrodite spermatogenesis and the maternal effects of fem-3 on embryonic sex determination. Whereas loss-of-function mutants in fem-3 produce only oocytes, hermaphrodites carrying any of nine fem-3 gain-of-function (gf) mutations make none; instead sperm are produced continuously and in vast excess over wild-type amounts. Genetic analyses suggest that fem-3(gf) mutations have escaped a negative control required for the switch to oogenesis. Here we report that all nine fem-3(gf) mutants carry sequence alterations in the fem-3 3' untranslated region (3' UTR). There is no increase in the steady-state level of fem-3(gf) RNA over wild-type, but there is an increase in the polyadenylation of fem-3(gf) RNA that is coincident with the unregulated fem-3 activity. Results of a titration experiment support the hypothesis that a regulatory factor may bind the fem-3 3' UTR. We speculate that fem-3 RNA is regulated through its 3' UTR by binding a factor that inhibits translation, and discuss the idea that this control may be part of a more general regulation of maternal RNAs.

Animals↗
PubMed2006

Co expression of SCF and KIT in gastrointestinal stromal tumours (GISTs) suggests an autocrine/paracrine mechanism.

KIT is a tyrosine kinase receptor expressed by several tumours, which has for specific ligand the stem cell factor (SCF). KIT is the main oncogene in gastrointestinal stromal tumours (GISTs), and gain-of-function KIT mutations are present in 70% of these tumours. The aim of the study was to measure and investigate the mechanisms of KIT activation in 80 KIT-positive GIST patients. KIT activation was quantified by detecting phosphotyrosine residues in Western blotting. SCF production was determined by reverse transcriptase-PCR, ELISA and/or immunohistochemistry. Primary cultures established from three GISTs were also analysed. The results show that KIT activation was detected in all cases, even in absence of KIT mutations. The fraction of activated KIT was not correlated with the mutational status of GISTs. Membrane and soluble isoforms of SCF mRNA were present in all GISTs analysed. Additionally, SCF was also detected in up to 93% of GISTs, and seen to be present within GIST cells. Likewise, the two SCF mRNA isoforms were found to be expressed in GIST-derived primary cultures. Thus, KIT activation in GISTs may in part result from the presence of SCF within the tumours.

Autocrine Communication↗
PubMed2001

Kit signaling and negative regulation of daunorubicin-induced apoptosis: role of phospholipase Cgamma.

Previous studies have demonstrated that activation of Kit by stem cell factor (SCF), its natural ligand, or by gain-of-function point mutation in its intracellular domain, confers significant protection against apoptosis induced by growth factor deprivation or radiation. However, the effects of Kit activation on the cellular response to anti-tumor agents have not been so extensively documented. This study shows that daunorubicin-induced apoptosis and cytotoxicity were reduced in the murine Ba/F3 cells transfected with Kit (Ba/F3-Kit) in the presence of SCF and in Ba/F3 cells transfected with a constitutively active Kit variant (Ba/F3-KitDelta27), compared to either parental Ba/F3 (Ba/F3-wt) or unstimulated Ba/F3-Kit cells. In Ba/F3-wt and in Ba/F3-Kit cells, daunorubicin stimulated within 8-15 min neutral sphingomyelinase and ceramide production but not in SCF-stimulated Ba/F3-Kit or in Ba/F3-KitDelta27 whereas all Ba/F3 cells were equally sensitive to exogenous cell-permeant C6-ceramide. In Ba/F3-Kit, SCF-induced Kit activation resulted in a rapid phospholipase Cgamma (PLCgamma) tyrosine phosphorylation followed by diacylglycerol release and protein kinase C (PKC) stimulation. U-73122, a PLCgamma inhibitor, not only blocked diacylglycerol production and PKC stimulation but also restored daunorubicin-induced sphingomyelinase stimulation, ceramide production, and apoptosis. These results suggest that Kit activation results in PLCgamma-mediated PKC-dependent sphingomyelinase inhibition which contributes to drug resistance in Kit-related malignancies.

Animals↗
PubMed2000

SPINK1/PSTI polymorphisms act as disease modifiers in familial and idiopathic chronic pancreatitis.

BACKGROUND & AIMS: Gain-of-function trypsin mutations cause acute pancreatitis and chronic pancreatitis. Loss of trypsin inhibitor function may have similar effects. We investigated the prevalence of SPINK1 (PSTI) mutations in familial pancreatitis, idiopathic chronic pancreatitis, and controls. METHODS: Genetic-linkage studies were performed in 5 familial pancreatitis families. The entire SPINK1 gene was sequenced in 112 affected individuals and 95 control DNA samples, and exon 3 was sequenced in 95 additional controls. X-ray crystallography-based model building and statistical studies were performed. RESULTS: Significant linkage between pancreatitis and 5q31.1-2 was excluded. Novel SPINK1 mutations, one D50E mutation, one IVS3+125 C>A, and five IVS3+184 T>A intronic polymorphisms were identified. The N34S and P55S mutations were observed in 29 of 112 patients (25%) as N34S/N34S (n = 7), N34S/wt (n = 19), N34S/P55S (n = 2), and N34S/D50E (n = 1). Three hundred eighty control alleles revealed 3 N34S (0.77%), 2 P55S (0.53%), and no D50E mutations. Age of disease onset and severity were similar between homozygous and heterozygous patients. Structural modeling revealed several possible pathophysiologic mechanisms for the N34S mutation. CONCLUSIONS: SPINK1 mutations are common in the population (approximately 2%), but are clearly associated with pancreatitis. The mutation-associated risk is low. Modeling and familial clustering suggest that SPINK1 mutations are disease modifying, possibly by lowering the threshold for pancreatitis from other genetic or environmental factors, but by themselves do not cause disease.

Amino Acid Sequence↗
PubMed2002

A tumor-specific kinase activity regulates the viral death protein Apoptin.

Apoptin, a chicken anemia virus-encoded protein, is thought to be activated by a general tumor-specific pathway, because it induces apoptosis in a large number of human tumor or transformed cells but not in their normal, healthy counterparts. Here, we show that Apoptin is phosphorylated robustly both in vitro and in vivo in tumor cells but negligibly in normal cells, and we map the site to threonine 108. A gain-of-function point mutation (T108E) conferred upon Apoptin the ability to accumulate in the nucleus and kill normal cells, implying that phosphorylation is a key regulator of the tumor-specific properties of Apoptin. An activity that could phosphorylate Apoptin on threonine 108 was found specifically in tumor and transformed cells from a variety of tissue origins, suggesting that activation of this kinase is generally associated with the cancerous or pre-cancerous state. Moreover, analyses of human tissue samples confirm that Apoptin kinase activity is detectable in primary malignancies but not in tissue derived from healthy individuals. Taken together, our results support a model whereby the dysregulation of the cellular pathway leading to the phosphorylation of Apoptin contributes to human tumorigenesis.

Amino Acid Sequence↗
PubMedDate not supplied

Behavioral genetics of caenorhabditis elegans unc-103-encoded erg-like K(+) channel.

The Caenorhabditis elegans unc-103 gene encodes a potassium channel whose sequence is most similar to the ether-a-go-go related gene (erg) type of K+ channels. We find that the n 500 and e 1597 gain-of-function (gf) mutations in unc-103 cause reduced excitation in most muscles, while loss-of-function (lf) mutations cause mild muscle hyper-excitability. Both gf alleles change the same residue near the cytoplasmic end of S6, consistent with this region regulating channel activation. We also report additional dominant-negative and lf alleles of unc-103 that can antagonize or reduce the function of both gf and wild-type alleles. The unc-103 locus contains 6 promoter regions that express unc-103 in different combinations of body-wall and sex-specific muscles, motor-, inter- and sensory-neurons. Each promoter drives transcripts containing a unique first exon, conferring sequence variability to the N-terminus of the UNC-103 protein, while three splice variants introduce variability into the UNC-103 C-terminus. unc-103(0) hermaphrodites prematurely lay embryos that would normally be retained in the uterus and lay eggs under conditions that inhibit egg-laying behavior. In the egg-laying circuit, unc-103 is expressed in vulval muscles and the HSN neurons from different promoters. Supplying the proper UNC-103 isoform to the vulval muscles is sufficient to restore regulation to egg-laying behavior.

Alleles↗
PubMed1994

A role for autophosphorylation revealed by activated alleles of FUS3, the yeast MAP kinase homolog.

We have isolated dominant gain-of-function (gf) mutations in FUS3, a Saccharomyces cerevisiae mitogen-activated protein (MAP) kinase homolog, that constitutively activate the yeast mating signal transduction pathway and confer hypersensitivity to mating pheromone. Surprisingly, the phenotypes of dominant FUS3gf mutations require the two protein kinases, STE7 and STE11. FUS3gf kinases are hyperphosphorylated in yeast independently of STE7. Consistent with this, FUS3gf kinases expressed in Escherichia coli exhibit an increased ability to autophosphorylate on tyrosine in vivo. FUS3gf mutations suppress the signal transduction defect of a severely catalytically impaired allele of STE7. This finding suggests that the tyrosine-phosphorylated form of FUS3 is a better substrate for activation by STE7. Furthermore, these results imply that the degree of autophosphorylation of a MAP kinase determines its threshold of sensitivity to upstream signals.

Alleles↗
PubMed1998

Repression by the 3' UTR of fem-3, a sex-determining gene, relies on a ubiquitous mog-dependent control in Caenorhabditis elegans.

The fem-3 sex-determining gene is repressed post-transcriptionally via a regulatory element in its 3' untranslated region (UTR) to achieve the switch from spermatogenesis to oogenesis in the Caenorhabditis elegans hermaphrodite germ line. In this paper, we investigate the fem-3 3' UTR control in somatic tissues using transgenic reporter assays, and we also identify six genes essential for this control. First, we find that a reporter transgene bearing a wild-type fem-3 3' UTR is repressed in somatic tissues, whereas one bearing a mutant fem-3 3' UTR is derepressed. Moreover, control by mutant 3' UTRs is temperature sensitive as predicted from the temperature sensitivity of the fem-3 gain-of-function (gf) mutations. Secondly, we find a fem-3 3' UTR RNA-binding activity in somatic tissues, in addition to the previously reported germ-line-specific binding by FBF. Thirdly, we find that each of six genes, mog-1-mog-6, is required for repression by the fem-3 3' UTR. Therefore, the mog genes not only affect the sperm/oocyte switch in the germ line, but also function in somatic tissues. We suggest that the mog genes may encode components of a ubiquitous machinery that is used for fem-3 3' UTR-mediated repression and the sperm/oocyte switch.

3' Untranslated Regions↗
PubMed2001

pitkin(D), a novel gain-of-function enhancer of position-effect variegation, affects chromatin regulation during oogenesis and early embryogenesis in Drosophila.

The vast majority of the >100 modifier genes of position-effect variegation (PEV) in Drosophila have been identified genetically as haplo-insufficient loci. Here, we describe pitkin(Dominant) (ptn(D)), a gain-of-function enhancer mutation of PEV. Its exceptionally strong enhancer effect is evident as elevated spreading of heterochromatin-induced gene silencing along euchromatic regions in variegating rearrangements. The ptn(D) mutation causes ectopic binding of the SU(VAR)3-9 heterochromatin protein at many euchromatic sites and, unlike other modifiers of PEV, it also affects stable position effects. Specifically, it induces silencing of white+ transgenes inserted at a wide variety of euchromatic sites. ptn(D) is associated with dominant female sterility. +/+ embryos produced by ptn(D)/+ females mated with wild-type males die at the end of embryogenesis, whereas the ptn(D)/+ sibling embryos arrest development at cleavage cycle 1-3, due to a combined effect of maternally provided mutant product and an early zygotic lethal effect of ptn(D). This is the earliest zygotic effect of a mutation so far reported in Drosophila. Germ-line mosaics show that ptn+ function is required for normal development in the female germ line. These results, together with effects on PEV and white+ transgenes, are consistent with the hypothesis that the ptn gene plays an important role in chromatin regulation during development of the female germ line and in early embryogenesis.

Animals↗
PubMed2003

Role of constitutively activated protein tyrosine kinases in malignant myeloproliferative disorders: an update.

Modern molecular technology helped identify more than 10 protein tyrosine kinases related to myeloid malignancies, which allowed the development of small molecule inhibitors targeting deregulated protein tyrosine kinase activity. Protein tyrosine kinase deregulation can occur as a consequence of fusion gene formation because of chromosomal translocations, or as distinct gain-of-function point mutations. Although the tyrosine kinase inhibitor imatinib mesylate (Gleevec) targeting the ABL protein tyrosine kinase has revolutionized current chronic myeloid leukemia therapy, it became rapidly evident that overcoming the multiple cellular resistance mechanisms will be very challenging. To develop efficient therapeutic alternatives, one must understand the complex signal transduction mechanisms involved in transformation by deregulated protein tyrosine kinases. This article reviews the most recently identified molecular mechanisms involved in cell transformation by the BCR/ABL protein tyrosine kinase fusion and presents new members of the increasing family of deregulated protein tyrosine kinases involved in myeloproliferative disorders. In addition, the article discusses new, promising small molecule protein tyrosine kinase inhibitors and the molecular mechanism that may lead to resistance to these drugs. Finally, the article highlights putative alternative strategies that could be used to block signal transduction pathways of deregulated protein tyrosine kinase activity.

Cell Transformation, Neoplastic↗
PubMed1998

Sites of regulatory interaction between calcium ATPases and phospholamban.

Phospholamban (PLN) is a 52-amino acid, integral membrane protein that interacts with and reversibly inhibits the activity of the cardiac sarcoplasmic reticulum Ca2+ ATPase (SERCA2a). We have used site-directed mutagenesis to analyze the sites of interaction between PLN and SERCA2a. First, we used chimera formation between SERCA2a and SERCA3 (which is weakly inhibited by PLN) to determine the interacting residues in cytoplasmic sequences of SERCA2 and PLN. Then, we expressed SERCA2a with the transmembrane sequence of PLN and demonstrated that the sites of inhibitory interaction are located in transmembrane sequences of the two proteins. We proposed that a four-base circuit involving noninhibitory cytoplasmic and inhibitory transmembrane sites in PLN and SERCA2a best describes the interaction. Recently, we have used alanine-scanning mutagenesis to show an asymmetric distribution of function in the transmembrane domain of PLN--one helical face interacts with PLN molecules in a pentamer, and the other interacts with SERCA2a. Gain of function by mutation of PLN-interacting residues indicates that the inhibitory species of PLN is a monomer. Thus regulatory steps include PLN dissociation, PLN/SERCA2a inhibitory association, and PLN/SERCA2a dissociation induced by phosphorylation of PLN (in the noninhibitory cytoplasmic domain) or by binding of Ca2+ by SERCA2a (in the inhibitory transmembrane domain).

Amino Acid Sequence↗
PubMed2006

Discovery of a novel shp2 protein tyrosine phosphatase inhibitor.

Shp2 is a nonreceptor protein tyrosine phosphatase (PTP) encoded by the PTPN11 gene. It is involved in growth factorinduced activation of mitogen-activated protein (MAP) kinases Erk1 and Erk2 (Erk1/2) and has been implicated in the pathogenicity of the oncogenic bacterium Helicobacter pylori. Moreover, gain-of-function Shp2 mutations have been found in childhood leukemias and Noonan syndrome. Thus, small molecule Shp2 PTP inhibitors are much needed reagents for evaluation of Shp2 as a therapeutic target and for chemical biology studies of Shp2 function. By screening the National Cancer Institute (NCI) Diversity Set chemical library, we identified 8-hydroxy-7-(6-sulfonaphthalen-2-yl)diazenyl-quinoline-5-sulfonic acid (NSC-87877) as a potent Shp2 PTP inhibitor. Molecular modeling and site-directed mutagenesis studies suggested that NSC-87877 binds to the catalytic cleft of Shp2 PTP. NSC-87877 cross-inhibited Shp1 in vitro, but it was selective for Shp2 over other PTPs (PTP1B, HePTP, DEP1, CD45, and LAR). It is noteworthy that NSC-87877 inhibited epidermal growth factor (EGF)-induced activation of Shp2 PTP, Ras, and Erk1/2 in cell cultures but did not block EGF-induced Gab1 tyrosine phosphorylation or Gab1-Shp2 association. Furthermore, NSC-87877 inhibited Erk1/2 activation by a Gab1-Shp2 chimera but did not affect the Shp2-independent Erk1/2 activation by phorbol 12-myristate 13-acetate. These results identified NSC-87877 as the first PTP inhibitor capable of inhibiting Shp2 PTP in cell cultures without a detectable off-target effect. Our study also provides the first pharmacological evidence that Shp2 mediates EGF-induced Erk1/2 MAP kinase activation.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Developmental changes due to long-distance movement of a homeobox fusion transcript in tomato.

Long-distance movement of RNA through the phloem is known to occur, but the functional importance of these transported RNAs has remained unclear. Grafting experiments with a naturally occurring dominant gain-of-function leaf mutation in tomato were used to demonstrate long-distance movement of mutant messenger RNA (mRNA) into wild-type scions. The stock-specific pattern of mRNA expression was graft transmissible, indicating that the mRNA accumulation pattern is inherent to the transcript and not attributable to the promoter. The translocated mRNA caused changes in leaf morphology of the wild-type scions, suggesting that the translocated RNA is functional.

Artificial Gene Fusion↗
PubMed2006

International Working Group (IWG) consensus criteria for treatment response in myelofibrosis with myeloid metaplasia, for the IWG for Myelofibrosis Research and Treatment (IWG-MRT).

Myelofibrosis with myeloid metaplasia (MMM) is a clinicopathologic entity characterized by stem cell-derived clonal myeloproliferation, ineffective erythropoiesis, extramedullary hematopoiesis, and bone marrow fibrosis and osteosclerosis. Patients with MMM have shortened survival and their quality of life is compromised by progressive anemia, marked hepatosplenomegaly, and severe constitutional symptoms including cachexia. After decades of frustration with ineffective therapy, patients are now being served by promising treatment approaches that include allogeneic hematopoietic stem cell transplantation and immunomodulatory drugs. Recent information regarding disease pathogenesis, including a contribution to the myeloproliferative disorder phenotype by a gain-of-function JAK2 mutation (JAK2(V617F)), has revived the prospect of targeted therapeutics as well as molecular monitoring of treatment response. Such progress calls for standardization of response criteria to accurately assess the value of new treatment modalities, to allow accurate comparison between studies, and to ensure that the definition of response reflects meaningful health outcome. Accordingly, an international panel of experts recently convened and delineated 3 response categories: complete remission (CR), partial remission (PR), and clinical improvement (CI). Bone marrow histologic and hematologic remissions characterize CR and CR/PR, respectively. The panel agreed that the CI response category is applicable only to patients with moderate to severe cytopenia or splenomegaly.

Disease Progression↗
PubMed1999

Functioning and nonfunctioning thyroid adenomas involve different molecular pathogenetic mechanisms.

The molecular biology of follicular cell growth in thyroid nodules is still poorly understood. Because gain-of-function (activating) mutations of the thyroid-stimulating hormone receptor (TShR) and/or Gs alpha genes may confer TSh-independent growth advantage to neoplastic thyroid cells, we searched for somatic mutations of these genes in a series of hyperfunctioning and nonfunctioning follicular thyroid adenomas specifically selected for their homogeneous gross anatomy (single nodule in an otherwise normal thyroid gland). TShR gene mutations were identified by direct sequencing of exons 9 and 10 of the TShR gene in genomic DNA obtained from surgical specimens. Codons 201 and 227 of the Gs alpha gene were also analyzed. At histology, all hyperfunctioning nodules and 13 of 15 nonfunctioning nodules were diagnosed as follicular adenomas. Two nonfunctioning thyroid nodules, although showing a prevalent microfollicular pattern of growth, had histological features indicating malignant transformation (a minimally invasive follicular carcinoma and a focal papillary carcinoma). Activating mutations of the TShR gene were found in 12 of 15 hyperfunctioning follicular thyroid adenomas. In one hyperfunctioning adenoma, which was negative for TShR mutations, a mutation in codon 227 of the Gs alpha gene was identified. At variance with hyperfunctioning thyroid adenomas, no mutation of the TShR or Gs alpha genes was detected in nonfunctioning thyroid nodules. In conclusion, our findings clearly define a different molecular pathogenetic mechanism in hyperfunctioning and nonfunctioning follicular thyroid adenomas. Activation of the cAMP cascade, which leads to proliferation but maintains differentiation of follicular thyroid cells, typically occurs in hyperfunctioning thyroid adenomas. Oncogenes other than the TShR and Gs alpha genes are probably involved in nonfunctioning follicular adenomas.

Adenoma↗
PubMed2003

The Snail-like CES-1 protein of C. elegans can block the expression of the BH3-only cell-death activator gene egl-1 by antagonizing the function of bHLH proteins.

The NSM cells of the nematode Caenorhabditis elegans differentiate into serotonergic neurons, while their sisters, the NSM sister cells, undergo programmed cell death during embryogenesis. The programmed death of the NSM sister cells is dependent on the cell-death activator EGL-1, a BH3-only protein required for programmed cell death in C. elegans, and can be prevented by a gain-of-function (gf) mutation in the cell-death specification gene ces-1, which encodes a Snail-like DNA-binding protein. Here, we show that the genes hlh-2 and hlh-3, which encode a Daughterless-like and an Achaete-scute-like bHLH protein, respectively, are required to kill the NSM sister cells. A heterodimer composed of HLH-2 and HLH-3, HLH-2/HLH-3, binds to Snail-binding sites/E-boxes in a cis-regulatory region of the egl-1 locus in vitro that is required for the death of the NSM sister cells in vivo. Hence, we propose that HLH-2/HLH-3 is a direct, cell-type specific activator of egl-1 transcription. Furthermore, the Snail-like CES-1 protein can block the death of the NSM sister cells by acting through the same Snail-binding sites/E-boxes in the egl-1 locus. In ces-1(gf) animals, CES-1 might therefore prevent the death of the NSM sister cells by successfully competing with HLH-2/HLH-3 for binding to the egl-1 locus.

Animals↗
PubMed2005

Dynamic force spectroscopy of glycoprotein Ib-IX and von Willebrand factor.

The first stage in hemostasis is the binding of the platelet membrane receptor glycoprotein (GP) Ib-IX complex to the A1 domain of von Willebrand factor in the subendothelium. A bleeding disorder associated with this interaction is platelet-type von Willebrand disease, which results from gain-of-function (GOF) mutations in amino acid residues 233 or 239 of the GP Ibalpha subunit of GP Ib-IX. Using optical tweezers and a quadrant photodetector, we investigated the binding of A1 to GOF and loss-of-function mutants of GP Ibalpha with mutations in the region containing the two known naturally occurring mutations. By dynamically measuring unbinding force profiles at loading rates ranging from 200-20,000 pN/s, we found that the bond strengths between A1 and GP Ibalpha GOF mutants (233, 235, 237, and 239) were significantly greater than the A1/wild-type GP Ib-IX bond at all loading rates examined (p < 0.05). In addition, mutants 231 and 232 exhibited significantly lower bond strengths with A1 than the wild-type receptors (p < 0.05). We computed unloaded dissociation rate constant (k(off)(0)) values for interactions involving mutant and wild-type GP Ib-IX receptors with A1 and found the A1/wild-type GP Ib-IX k(off)(0) value of 5.47 +/- 0.25 s(-1) to be significantly greater than the GOF k(off)(0) values and significantly less than the loss-of-function k(off)(0) values. Our data illustrate the importance of the bond kinetics associated with the VWF/GP Ib-IX interaction in hemostasis and also demonstrate the drastic changes in binding that can occur when only a single amino acid of GP Ibalpha is altered.

Amino Acid Sequence↗