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PubMed1996

Biochemical characterization of a new disintegrin, flavostatin, isolated from Trimeresurus flavoviridis venom.

We biochemically characterized a new disintegrin, flavostatin, isolated from Trimeresurus flavoviridis venom. Flavostatin inhibited ADP-, collagen-, and thrombin receptor agonist peptide-induced platelet aggregation in human platelet-rich plasma (IC50 range: 59 to 111 nM) and blocked the binding of biotinylated human fibrinogen to purified GPIIb/IIIa with an inhibitory potency 31,000-fold higher than that of Arg-Gly-Asp-Ser (RGDS). Flavostatin strongly inhibited high-shear-stress-induced platelet aggregation in platelet-rich plasma (PRP) with an IC50 value of 188 nM. Fluorescein isothiocyanate (FITC)-conjugated flavostatin saturably bound to unstimulated and ADP-stimulated washed platelets with high affinity (Kd values: 38 and 21 nM, respectively); the corresponding number of binding sites was 86460 and 79192 per platelet. In competition experiments with several glycoprotein IIb/IIIa antagonists, the binding of FITC-conjugated flavostatin to platelets was completely inhibited by ReoPro, triflavin, TP9201, MK383 and GR144053, but not by YM207, YM337 and B6A3.

Amino Acid Sequence↗
PubMed1978

Purification and characterization of the anticoagulant principle of Trimeresurus mucrosquamatus venom.

By means of CM-Sephadex column chromatography, Trimeresurus mucrosquamatus venom was separated into 20 fractions. Fraction XX had the marked anticoagulant action. This fraction was refractionated three times on Sephadex G-75, and a single peak was obtained. The patterns of microzone and disc electrophoresis also showed a single band. A single, symmetrical boundary with a value of 1.61 S was obtained by ultracentrifugation. It was a single peptide chain with a molecular weight of 11 700. The isoelectric point was higher than pH 10. The anticoagulant principle possessed phospholipase A activity and was calcium ion dependent. It did not possess proteolytic, tosyl-L-arginine methyl ester esterase, phosphodiesterase and alkaline phosphomonoesterase activities of the crude venom. The phospholipase A activity was heat-labile at pH 7.4, but was heat-stable at pH 5.6. The anticoagulant activity was more resistant to heat treatment as compared with phospholipase A activity. The anitoagulant action of the purified principle was competitively inhibited by platelet phospholid, tissue thromboplastin and cephalin, and was neutralized by antiserum. The anticoagulant principle inhibited platelet aggregation induced by ADP. It did not destroy fibrinogen, Factor X, prothrombin and thrombin; nor did it induce fibrinolysis nor interfere with the interaction between thrombin and fibrinogen. It is concluded that the anticoagulant action of this phospholipase A was due to the inhibition of the activations of Factors X and II through the inactivation of the procoagulant activity of phospholipids mediated partly by phospholipid-binding activity of this venom enzyme and partly by its enzymatic hydrolysis of phospholipids.

Amino Acids↗
PubMed1980

A potent platelet aggregation inducer purified from Trimeresurus mucrosquamatus snake venom.

A non-coagulant platelet aggregation inducer (called platelet 'aggregoserpentin') was isolated from Trimeresurus mucrosquamatus snake venom by CM-Sephadex chromatography and purified by gel filtration. It was homogeneous as judged by the ultracentrifugal analysis and electrophoresis on polyacrylamide gel and cellulose acetate membrane. The molecular weight was estimated to be 68 000 as judged by the SDS-polyacrylamide gel electrophoresis and gel filtration on Sephadex G-75. The ultracentrifugal analysis gave 3.19 Svedberg units. It was a protein-polysaccharide complex containing 340 amino acid residues and 50% carbohydrate per molecule. The isoelectric point was pH 5.4. It did not possess any of the hydrolase enzymatic properties which were found in the crude venom. The minimal concentration of 'aggregoserpentin' necessary to induce platelet aggregation was 10 ng/ml, about one four-hundredth of that of the crude venom. It did not cause lysis of platelets because lactate dehydrogenase was not found in supernatant after complete aggregation. An intravenous injection of 'aggregoserpentin' (35 microgram/kg) into rabbit ear marginal vein caused marked decrease of platelet number to approx. 10-20% of that of the control.

Animals↗
PubMed1983

Potent platelet aggregation inhibitor from Trimeresurus gramineus snake venom.

Using DEAE-Sephadex A-50 column chromatography and gel filtration, a potent platelet aggregation inhibitor from Trimeresurus gramineus venom was purified. It was an acidic phospholipase A, rich in aspartic acid, glutamic acid and half-cystine, with an isoelectric point of 3.6. At a concentration of 10 micrograms/ml, the purified inhibitor showed a marked inhibitory effect on platelet aggregations induced by adenosine diphosphate, collagen, sodium arachidonate and ionophore A-23187 in rabbit platelet-rich plasma, washed platelet suspension, as well as in thrombin-degranulated platelet suspension. The ID50 of this venom inhibitor was about 2.5-5 micrograms/ml in platelet aggregations induced by all these aggregation inducers. The action of this inhibitor could be partially antagonized by phosphatidylethanolamine. High concentration of Ca2+ (5 mM) did not reverse the inhibitory action even in the presence of ionophore A-23187. The [14C]serotonin release induced by sodium arachidonate and thrombin was unaffected. Malonic dialdehyde formation induced by these aggregation inducers remained unchanged. Basal and prostaglandin E1-stimulated cAMP levels were not altered by this inhibitor. No lactate dehydrogenase was released even at a concentration of 62.5 micrograms/ml. Polylysine-induced platelet agglutination was not affected. beta-Mercaptoethanol inactivated both its phospholipase A enzymatic and platelet inhibitory activities, while p-bromophenacyl bromide only inactivated the former activity. The possibility of acting on a common final step of platelet aggregation, i.e. the intercellular adhesion between the activated platelets, was proposed.

Animals↗
PubMed1983

A potent platelet aggregation inducer from Trimeresurus gramineus snake venom.

A potent platelet aggregation inducer (platelet aggregoserpentin) was purified from Trimeresurus gramineus snake venom by DEAE-Sephadex A-50 and Sephacryl S-300 column chromatography. It was homogeneous as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It elicited dose-dependently platelet aggregation and serotonin release reaction in rabbit platelet-rich plasma and platelet suspension. Exogenous calcium was required for its activity. Creatine phosphate/creatine phosphokinase and apyrase showed no significant inhibitory effect on aggregoserpentin-induced platelet aggregation in platelet suspension. Aggregoserpentin induced aggregation in ADP-refractory platelet-rich plasma. It caused no detectable malonic dialdehyde formation in the process of platelet aggregation. Indomethacin did not inhibit aggregoserpentin-induced platelet aggregation. Mepacrine abolished preferentially its aggregating activity, while prostaglandin E1 completely blocked both aggregoserpentin-induced aggregation and release reaction. Furthermore, platelet aggregoserpentin lowered basal and prostaglandin E1-stimulated cAMP levels in platelet suspension. Nitroprusside inhibited both its aggregating and releasing activity, while verapamil preferentially blocked its aggregating activity. It is concluded that aggregoserpentin activated platelets through lowering cAMP levels or the activation of endogenous phospholipase A2, resulting in the formation of platelet activating factor, but not of prostaglandins.

Adenine Nucleotides↗
PubMed1985

Isolation and characterization of hemorrhagic factors a and b from the venom of the Chinese habu snake (Trimeresurus mucrosquamatus).

Hemorrhagic factors a and b were isolated from Trimeresurus mucrosquamatus venom by Sephadex G-100, CM-Sephadex C-50 and DEAE-Sephacel column chromatographies. The hemorrhagic factors were homogeneous, as established by a single band on acrylamide gel electrophoresis, isoelectric focusing and sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. Molecular weights of 15 000 and 27 000 were found for hemorrhagic factors a and b, respectively. Factor a possesses proteolytic activity hydrolyzing the His(10)-Leu(11), Tyr(16)-Leu(17) and Arg(22)-Gly(23) bonds of oxidized insulin B chain, whereas, factor b hydrolyzed only the Ala(14)-Leu(15) bond. Hemorrhagic activity of these hemorrhagic factors was inhibited by ethylenediaminetetraacetic acid, 1,10-phenanthroline or p-chloromercuribenzoate, but not by soybean trypsin inhibitor or diisopropyl fluorophosphate. The hemorrhagic factors were injected into the skin of the back of albino rabbits, and the minimum hemorrhagic dose of factors a and b was 1.7 and 2.3 micrograms, respectively. These purified hemorrhagic factors were not lethal at 15 micrograms/g in mice. Factor a hydrolyzed the B beta chain of fibrinogen, while factor b hydrolyzed the A alpha chain. Hemorrhagic factor a was shown to differ immunologically from factor b. Factors a and b produced systemic hemorrhage in internal organs such as the heart and stomach of mice. Moreover, factor b produced hemorrhage in the liver.

Animals↗
PubMed1987

Purification, characterization and substrate specificity of a basic proteinase in the venom of habu (Trimeresurus flavoviridis).

A basic proteinase was purified and characterized from the venom of Habu (Trimeresurus flavoviridis). Its molecular weight, isoelectric point and optimum pH were approx. 24,000, 9.2 and 9, respectively. Susceptibility to several reagents was examined. The proteinase had endopeptidase activity cleaving the Gly-Leu bond in synthetic peptides but no exopeptidase activity. It did not hydrolyze a peptide, Z-Gly-Pro-Leu-Gly-Pro, which had been a good substrate for the major proteinase in the venom. The proteinase cleaved oxidized insulin B chain at five positions: His10-Leu11, Ala14-Leu15, Tyr16-Leu17, Gly23-Phe24 and Phe24-Phe25. From the disappearance of intermediate peptides and the peptides accumulated, the order and the intensity of cleavage of these positions were determined, and the substrate specificity was compared with those hitherto described for hemorrhagic and nonhemorrhagic venom proteinases.

Animals↗
PubMed1985

Comparative study of three proteinases from the venom of the Chinese habu snake (Trimeresurus mucrosquamatus).

Three immunochemically distinct proteinases (P-1, 2 and 3) devoid of hemorrhagic activity were isolated from the lyophilized venom of Trimeresurus mucrosquamatus using column chromatography on Sephadex G-100, CM-Sephadex C-50, DEAE-Sephacel, CM-Cellulose and Bio-Rex 70. By these procedures, about 7.6, 7.3 and 8.2 mg of purified P-1, 2 and 3 may be obtained from 1 g of crude venom, respectively. The purified proteinases 1-3 were homogeneous by disc electrophoresis on polyacrylamide gel at pH 4.3, isoelectric focusing and by the presence of one precipitin line on immunodiffusion. The isoelectric point of P-1 was 8.1; P-2, 9.2; P-3, 9.8. The molecular weights of proteinases 1-3 were determined to be 23,000, 23,500 and 23,000, by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis, respectively. The purified proteinases 1-3 possessed caseinolytic and fibrinogenolytic activities. These activities were inhibited when the proteinases were incubated with the metal chelators ethylenediaminetetraacetic acid (EDTA), 1,10-phenanthroline or cysteine, but not with egg white trypsin inhibitor (EWTI) or soybean trypsin inhibitor (SBTI). P-1 cleaved the B beta-chain of fibrinogen first and then the A alpha-chain, whereas P-2 and 3 cleaved the A alpha-chain first and then the B beta-chain. However, these three proteinases did not hydrolyze the gamma-chain.

Amino Acids↗
PubMed1986

Comparative study of four arginine ester hydrolases, ME-1, 2, 3 and 4 from the venom of Trimeresurus mucrosquamatus (the Chinese habu snake).

Four arginine ester hydrolases, ME-1, 2, 3 and 4 from the venom of Trimeresurus mucrosquamatus had been isolated and characterized by Sugihara et al. (1980, 1981, 1982, 1983). Immunologically, ME-1, 2, 3 and 4 are identical. The four enzymes hydrolyzed Pro-Phe-Arg-MCA and z-Phe-Arg-MCA. Furthermore, ME-2 slightly hydrolyzed Boc-Val-Pro-Arg-MCA, Boc-Phe-Ser-Arg-MCA and Boc-Ile-Glu-Gly-Arg-MCA. ME-1 cleaved almost simultaneously the Arg(22)-Gly(23) and Phe(25)-Tyr(26) bond of oxidized insulin B chain. ME-2 and 3 also hydrolyzed the same bond of insulin B chain, but the activity was not as potent as ME-1. ME-4 did not cleave the substrate. The four enzymes hydrolyzed C-terminal of arginine in the biologically active peptides. Four arginine ester hydrolases showed fibrinogenolytic activity. ME-1 and 2 first cleaved B beta-chain and then A alpha-chain. On the contrary, ME-3 and 4 cleaved A alpha- and B beta-chain simultaneously. The four enzymes also hydrolyzed fibrinogen in plasma cleaving B beta- and gamma-chain and slightly digesting A alpha-chain. The various inhibitors affected TAME (tosyl-arginine-methylester) and the fibrinogen hydrolytic activity of the four enzymes. All four enzymes had fibrinolytic activity.

Amino Acid Sequence↗
PubMed1987

Substance P-like immunoreactive fibers in the trigeminal sensory nuclei of the pit viper, Trimeresurus flavoviridis.

Substance P-like immunoreactive nerve fibres were located in the trigeminal sensory system of the infrared-sensitive snake, Trimeresurus flavoviridis, using the immunohistochemical method. There are two trigeminal sensory systems in the medulla of this animal: the descending nucleus and the lateral descending nucleus. The descending nucleus is equivalent to the trigeminal spinal nucleus in other vertebrates, and the lateral descending nucleus is a special trigeminal sensory nucleus belonging to the infrared sensory system. In the present study we determined that the lateral descending nucleus is completely ensheathed by large numbers of substance P-like immunoreactive fibers. The distribution of these fibers seems to be similar to that of the thin vagal unmyelinated fibers, rather than to that of the thick trigeminal myelinated fibers. More substance P-like immunoreactive nerve fibers were observed in the lateral descending tract than in the descending tract. Almost no dense substance P-like immunoreactive fibers were found in these tracts rostral to the lateral descending nucleus or rostral to the subnucleus caudalis of the descending nucleus. The substance P-like immunoreactive fibers in the lateral descending tract extended to those of Lissauer's tract of the spinal cord, and the substance P-like immunoreactive fibers surrounding the Lissauer's tract were similar in appearance to those of the lateral descending nucleus. This nucleus seems to have developed from the elements existing in Lissauer's tract, and also to have a similar modulating function. The primary nucleus of the infrared sensory system is the most substance P-like immunoreactive nucleus in the trigeminal sensory system of this animal. Even in the trigeminal sensory system, substance P-like immunoreactive fibers seem not to be related solely to the nociceptive sensation.

Animals↗
PubMed2003

Molecular characterization of Trimeresurus stejnegeri venom L-amino acid oxidase with potential anti-HIV activity.

A novel L-amino acid oxidase, named TSV-LAO, has been purified and cloned from the snake Trimeresurus stejnegeri. Fifty percentage cytotoxic concentrations (CC50) of TSV-LAO on C8166 cells were 24 and 390 nM in the absence or presence of catalase (400 nM), respectively. However, at concentrations that showed little effect on cell viability, TSV-LAO displayed dose dependent inhibition on HIV-1 infection and replication. The antiviral selectivity indexes (CC50/EC50) were 16 and 6, respectively, corresponding to the measurements of syncytium formation and HIV-1 p24 antigen expression. Interestingly, the presence of catalase resulted in an increase of its antiviral selectivity to 52 and 38. Under the same conditions, no anti-HIV-1 activity was observed by exogenous addition of H2O2. The complete amino acid sequence of TSV-LAO, as deduced from its cDNA, exhibits a high degree of sequence identity with other snake venom LAOs.

Amino Acid Oxidoreductases↗
PubMed2006

Cloning of two novel P-III class metalloproteinases from Trimeresurus stejnegeri venom gland.

Hemorrhagic toxins are widely distributed in viperid and crotalid snake venoms. Envenomation of Trimeresurus stejnegeri, a member of Crotalidae family, caused potent systemic and local hemorrhage. Up to now, there is no report on hemorrhage toxins from this venom. In this work, we cloned two cDNAs of P-III metalloproteinase precursors, designated as stejnihagin-A and stejnihagin-B, respectively, from T. stejnegeri venom gland. Both cDNAs encode an opening reading frame of 600 amino acid residues, containing a signal sequence, a proprotein domain, a metalloproteinase domain, a disintegrin-like domain and a cystetine-rich domain. Sequence analysis suggested that these two sequences shared highest similarity to the hemorrhagic toxin HR1b from T. flavoviridis. Aligning the deduced mature protein sequences of stejnihagin-A and stejnihagin-B with other snake venom metalloproteinases (SVMPs), we observed that stejnihagin-A and stejnihagin-B, together with HR1b shared the common cysteinyl residue at the position 100 in the metalloproteinase domain. In combination with the phylogenetic analysis, we presumed that stejnihagin-A, stejnihagin-B and HR1b might constitute a novel subclass of P-III SVMPs, named P-IIIc.

Amino Acid Sequence↗
PubMed1984

Rapid method for separation and purification of four isoenzymes of phosphodiesterase from Trimeresurus flavoviridis (Habu snake) venom.

Four isoenzymes of phosphodiesterase were identified in Trimeresurus flavoviridis venom. A rapid and highly reproducible column chromatographic procedure on CM-Sephadex C-25, QAE-Sephadex A-25 and Sephadex G-100 was developed for the purification of these isoenzymes with a yield of 83%. All four isoenzymes are metalloglycoproteins having negligible amounts of phosphomonoesterase activity.

Animals↗
PubMed2001

Purification and characterization of jerdofibrase, a serine protease from the venom of Trimeresurus jerdonii snake.

A fibrin(ogen)olytic serine protease from Trimeresurus jerdonii venom was identified and purified to SDS-polyacrylamide gel electrophoresis homogeneity. It is a single chain polypeptide with a molecular weight of 32kDa under reduced condition and 28kDa under non-reduced condition, respectively. The venom protease catalysed the hydrolysis of some chromogenic substrates such as S2238, S2160, S2302 and S2251. It degraded Bbeta-chain of human fibrinogen preferentially. Also the enzyme degraded fibrin directly. Its enzymatic activity was completely inhibited by phenylmethylsulfonyl fluoride (PMSF), but not affected by EDTA. That suggested it was a serine protease. N-terminal sequence of the purified component showed high homology with other snake venom serine proteases.

Amino Acid Sequence↗
PubMed1997

Cloning and expression of a cysteine-rich venom protein from Trimeresurus mucrosquamatus (Taiwan habu).

A full-length cDNA for cysteine-rich venom protein (CRVP) was constructed by immunoscreening and 5'-rapid amplification of cDNA ends from a cDNA library of venom gland of Trimeresurus mucrosquamatus. The predicted CRVP consisted of 183 amino acid residues including a putative signal peptide of 21 residues. Northern blot hybridization suggested the tissue-specific expression in venom gland and its corresponding length of cDNA. The predicted amino acid sequence of CRVP was homologous to a rat epididymal metalloprotein and a lizard helothermine. Amino acid sequence analysis suggested that CRVP may be a venom metalloprotein targeted against ryanodine receptors and Ca2+ release. Moreover, CRVP expressed in Escherichia coli exhibited the same antigenicity as their native venom forms of T. mucrosquamatus. This is the first report in the cloning and expression of a CRVP from the venom gland of T. mucrosquamatus.

Amino Acid Sequence↗
PubMed1998

Characterization of a fibrinogen-clotting enzyme from Trimeresurus stejnegeri venom, and comparative study with other venom proteases.

Trimeresurus stejnegeri venom which contains TSV-PA (a specific plasminogen activator sharing 60-70% sequence homology with venom fibrinogen-clotting enzymes), also possesses fibrinogen-clotting activity in vitro. A fibrinogen-clotting enzyme (stejnobin) has been purified to homogeneity by gel filtration and ion-exchange chromatography on a Mono-Q column. It is a single-chain glycoprotein with a mol. wt of 44,000. The NH2-terminal amino acid sequence of stejnobin shows great homology with venom fibrinogen-clotting enzymes and TSV-PA. Like TSV-PA, stejnobin was able to hydrolyse several chromogenic substrates. Comparative study of substrate specificities of stejnobin and other venom proteases purified in our laboratory was carried out on five chromogenic substrates. Stejnobin clotted human fibrinogen with a specific activity of 122 NIH thrombin-equivalent units/mg protein. However, stejnobin did not act on other blood coagulation factors, such as factor X, prothrombin and plasminogen. Diisopropyl fluorophosphate and phenylmethanesulfonyl fluoride inhibited its activity, whereas ethylenediamine tetracetic acid had no effect on it, indicating that it is a serine protease. Although stejnobin showed strong immunological cross-reaction with polyclonal antibodies raised against TSV-PA, it was interesting to observe that, unlike the case of TSV-PA, these antibodies did not inhibit the amidolytic and fibrinogen-clotting activities of stejnobin.

Blood Coagulation↗
PubMed1991

Identification of the disulfide bond pattern in albolabrin, an RGD-containing peptide from the venom of Trimeresurus albolabris: significance for the expression of platelet aggregation inhibitory activity.

Albolabrin is a 73 amino acid peptide isolated from the venom of Trimeresurus albolabris. It contains an RGD sequence and 12 cysteines and is a potent inhibitor of both platelet aggregation and fibrinogen binding to the GPIIb/IIIa complex. This protein shows a high degree of analogy (primarily due to the alignment of all cysteines and the RGD) with a number of other viper venom proteins which inhibit cell adhesion and platelet aggregation and are referred to as disintegrins: rhodostomin, trigramin, flavoridin, applagin, elegantin, and batroxostatin. In this study, we found that the reduction and vinylpyridylethylation of albolabrin and flavoridin decreased their platelet aggregation inhibitory activity approximately 40-50 times. It can be postulated that the higher potency of native and reduced flavoridin as compared to albolabrin depends on the substitution of the Asp of albolabrin with a Phe at the C-terminal end of the RGD in flavoridin. The activity of a synthetic C-terminal peptide derived from flavoridin (residues 35-65) containing four cysteines was about 75 times lower than that of the original flavoridin. The substitution of a pair of cysteine residues with alanines in this peptide resulted in further loss of activity. In order to identify the disulfide bonds in albolabrin, the molecule was digested consecutively by trypsin and porcine pancreatic elastase. Peptides resulting from this digestion were isolated by reverse-phase HPLC and identified by amino acid composition and mass spectrometry.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Diphosphate↗
PubMed1996

Binding of a novel 50-kilodalton alboaggregin from Trimeresurus albolabris and related viper venom proteins to the platelet membrane glycoprotein Ib-IX-V complex. Effect on platelet aggregation and glycoprotein Ib-mediated platelet activation.

Binding of the multimeric adhesive glycoprotein, von Willebrand Factor (vWF), to the platelet membrane glycoprotein (GP) Ib-IX-V complex mediates platelet adhesion and initiates signal transduction leading to platelet activation. Recently described viper venom proteins that bind to the GP Ib alpha-chain and inhibit vWF binding provide novel probes for studying receptor function. We have purified a 50-kDa form of alboaggregin from the white-lipped tree viper (Trimeresurus albolabris) and two 25-kDa proteins, CHH-A and CHH-B, from the timber rattlesnake (Crotalus horridus horridus) in addition to a previously described 25-kDa alboaggregin and echicetin. Complete or partial amino acid sequencing of CHH-A, CHH-B, and 50-kDa alboaggregin and cross-reactivity of these proteins with an anti-botrocetin antiserum confirmed that they were disulfide-linked heterodimers or higher multimers of the C-type lectin protein family. These proteins, together with 25-kDa alboaggregin and echicetin, specifically bound to GP Ib alpha within the N-terminal peptide domain, His-1-Glu-282, and inhibited vWF binding with comparable IC50 values (approximately 0.2 microgram/mL). However, cross-blocking studies between these structurally related proteins and anti-GP Ib alpha monoclonal antibodies demonstrated that the venom protein binding sites were not congruent. Further, the 50-kDa alboaggregin, but not the other venom proteins, potently induced platelet activation as assessed by dense granule serotonin release or elevation of cytosolic ionized calcium. Treatment of platelets with the 50-kDa alboaggregin was associated with activation of protein kinase C and tyrosine kinase(s), resulting in a platelet protein phosphorylation profile similar to that seen on shear-stress-induced vWF binding to platelets. These results suggest that the 50-kDa alboaggregin induces cytoplasmic signaling coincident with its binding to the GP Ib-IX-V complex and provides a potentially useful probe for studying the mechanism of vWF-dependent platelet activation.

Amino Acid Sequence↗