1
|
Barber CM, Rusmili MRA, Hodgson WC. Isolation and Pharmacological Characterization of α-Elapitoxin-Ot1a, a Short-Chain Postsynaptic Neurotoxin from the Venom of the Western Desert Taipan, Oxyuranus temporalis. Toxins (Basel) 2016; 8:toxins8030058. [PMID: 26938558 PMCID: PMC4810203 DOI: 10.3390/toxins8030058] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 02/19/2016] [Accepted: 02/19/2016] [Indexed: 11/16/2022] Open
Abstract
Taipans (Oxyuranus spp.) are elapids with highly potent venoms containing presynaptic (β) and postsynaptic (α) neurotoxins. O. temporalis (Western Desert taipan), a newly discovered member of this genus, has been shown to possess venom which displays marked in vitro neurotoxicity. No components have been isolated from this venom. We describe the characterization of α-elapitoxin-Ot1a (α-EPTX-Ot1a; 6712 Da), a short-chain postsynaptic neurotoxin, which accounts for approximately 30% of O. temporalis venom. α-Elapitoxin-Ot1a (0.1–1 µM) produced concentration-dependent inhibition of indirect-twitches, and abolished contractile responses to exogenous acetylcholine and carbachol, in the chick biventer cervicis nerve-muscle preparation. The inhibition of indirect twitches by α-elapitoxin-Ot1a (1 µM) was not reversed by washing the tissue. Prior addition of taipan antivenom (10 U/mL) delayed the neurotoxic effects of α-elapitoxin-Ot1a (1 µM) and markedly attenuated the neurotoxic effects of α-elapitoxin-Ot1a (0.1 µM). α-Elapitoxin-Ot1a displayed pseudo-irreversible antagonism of concentration-response curves to carbachol with a pA2 value of 8.02 ± 0.05. De novo sequencing revealed the main sequence of the short-chain postsynaptic neurotoxin (i.e., α-elapitoxin-Ot1a) as well as three other isoforms found in O. temporalis venom. α-Elapitoxin-Ot1a shows high sequence similarity (i.e., >87%) with other taipan short-chain postsynaptic neurotoxins.
Collapse
Affiliation(s)
- Carmel M Barber
- Monash Venom Group, Department of Pharmacology, Monash University, Clayton, VIC 3168, Australia.
| | - Muhamad Rusdi Ahmad Rusmili
- Monash Venom Group, Department of Pharmacology, Monash University, Clayton, VIC 3168, Australia.
- Department of Basic Medical Sciences, Kulliyyah of Pharmacy, International Islamic University Malaysia, Bandar Indera Mahkota 23800, Malaysia.
| | - Wayne C Hodgson
- Monash Venom Group, Department of Pharmacology, Monash University, Clayton, VIC 3168, Australia.
| |
Collapse
|
2
|
Venomics of the Australian eastern brown snake ( Pseudonaja textilis ): Detection of new venom proteins and splicing variants. Toxicon 2015; 107:252-65. [DOI: 10.1016/j.toxicon.2015.06.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Revised: 06/08/2015] [Accepted: 06/11/2015] [Indexed: 01/28/2023]
|
3
|
Barber CM, Madaras F, Turnbull RK, Morley T, Dunstan N, Allen L, Kuchel T, Mirtschin P, Hodgson WC. Comparative studies of the venom of a new Taipan species, Oxyuranus temporalis, with other members of its genus. Toxins (Basel) 2014; 6:1979-95. [PMID: 24992081 PMCID: PMC4113736 DOI: 10.3390/toxins6071979] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Revised: 06/11/2014] [Accepted: 06/16/2014] [Indexed: 11/16/2022] Open
Abstract
Taipans are highly venomous Australo-Papuan elapids. A new species of taipan, the Western Desert Taipan (Oxyuranus temporalis), has been discovered with two specimens housed in captivity at the Adelaide Zoo. This study is the first investigation of O. temporalis venom and seeks to characterise and compare the neurotoxicity, lethality and biochemical properties of O. temporalis venom with other taipan venoms. Analysis of O. temporalis venom using size-exclusion and reverse-phase HPLC indicated a markedly simplified "profile" compared to other taipan venoms. SDS-PAGE and agarose gel electrophoresis analysis also indicated a relatively simple composition. Murine LD50 studies showed that O. temporalis venom is less lethal than O. microlepidotus venom. Venoms were tested in vitro, using the chick biventer cervicis nerve-muscle preparation. Based on t90 values, O. temporalis venom is highly neurotoxic abolishing indirect twitches far more rapidly than other taipan venoms. O. temporalis venom also abolished responses to exogenous acetylcholine and carbachol, indicating the presence of postsynaptic neurotoxins. Prior administration of CSL Taipan antivenom (CSL Limited) neutralised the inhibitory effects of all taipan venoms. The results of this study suggest that the venom of the O. temporalis is highly neurotoxic in vitro and may contain procoagulant toxins, making this snake potentially dangerous to humans.
Collapse
Affiliation(s)
- Carmel M Barber
- Monash Venom Group, Department of Pharmacology, Faculty of Medicine, Nursing and Health Sciences, Monash University, Clayton, Victoria 3168, Australia.
| | - Frank Madaras
- Venom Science Pty Ltd, Tanunda, South Australia 5352, Australia.
| | - Richard K Turnbull
- SA Pathology, IMVS Veterinary Services, Gilles Plains, South Australia 5086, Australia.
| | - Terry Morley
- Adelaide Zoo, Adelaide, South Australia 5000, Australia.
| | - Nathan Dunstan
- Venom Supplies, Tanunda, South Australia, South Australia 5352, Australia.
| | - Luke Allen
- Venom Supplies, Tanunda, South Australia, South Australia 5352, Australia.
| | - Tim Kuchel
- SA Pathology, IMVS Veterinary Services, Gilles Plains, South Australia 5086, Australia.
| | - Peter Mirtschin
- Venom Science Pty Ltd, Tanunda, South Australia 5352, Australia.
| | - Wayne C Hodgson
- Monash Venom Group, Department of Pharmacology, Faculty of Medicine, Nursing and Health Sciences, Monash University, Clayton, Victoria 3168, Australia.
| |
Collapse
|
4
|
Abstract
Multicopper blue proteins, composed of several repetitive copper-binding domains similar to one-domain cupredoxin-like proteins, were found in almost all organisms. They are classified into the three different groups, based on their two-, three- or six-domain organization. We found orthologs of chordate six-domain copper-binding proteins in animals, plants, bacteria and archea. The phylogenetic analysis of 183 multicopper blue proteins and their copper-binding sites comparison make us think that all the modern six-domain blue proteins have originated from the common ancestral six-domain protein in the process of gene duplication and copper-binding sites loss as a result of amino acid substitutions.
Collapse
|
5
|
Bos MHA, Camire RM. A bipartite autoinhibitory region within the B-domain suppresses function in factor V. J Biol Chem 2012; 287:26342-51. [PMID: 22707727 DOI: 10.1074/jbc.m112.377168] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activation of blood coagulation factor V (FV) is a key reaction of hemostasis. FV circulates in plasma as an inactive procofactor, and proteolytic removal of a large central B-domain converts it to an active cofactor (FVa) for factor Xa (FXa). Here we show that two short evolutionary conserved segments of the B-domain, together termed the procofactor regulatory region, serve an essential autoinhibitory function. This newly identified motif consists of a basic (963-1008) and an acidic (1493-1537) region and defines the minimal sequence requirements to maintain FV as a procofactor. Our data suggest that dismantling this autoinhibitory region via deletion or proteolysis is the driving force to unveil a high affinity binding site(s) for FXa. These findings document an unexpected sequence-specific role for the B-domain by negatively regulating FV function and preventing activity of the procofactor. These new mechanistic insights point to new ways in which the FV procofactor to cofactor transition could be modulated to alter hemostasis.
Collapse
Affiliation(s)
- Mettine H A Bos
- Division of Hematology, The Children's Hospital of Philadelphia, PA 19104, USA
| | | |
Collapse
|
6
|
Procoagulant adaptation of a blood coagulation prothrombinase-like enzyme complex in australian elapid venom. Toxins (Basel) 2010; 2:1554-67. [PMID: 21127733 PMCID: PMC2994417 DOI: 10.3390/toxins2061554] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2010] [Revised: 06/04/2010] [Accepted: 06/17/2010] [Indexed: 11/17/2022] Open
Abstract
The macromolecular enzyme complex prothrombinase serves an indispensable role in blood coagulation as it catalyzes the conversion of prothrombin to thrombin, a key regulatory enzyme in the formation of a blood clot. Interestingly, a virtually identical enzyme complex is found in the venom of some Australian elapid snakes, which is composed of a cofactor factor Va-component and a serine protease factor Xa-like subunit. This review will provide an overview of the identification and characterization of the venom prothrombinase complex and will discuss the rationale for its powerful procoagulant nature responsible for the potent hemostatic toxicity of the elapid venom.
Collapse
|
7
|
|
8
|
Abstract
Activation of precursor proteins by specific and limited proteolysis is a hallmark of the hemostatic process. The homologous coagulation factors (F)V and FVIII circulate in an inactive, quiescent state in blood. In this so-called procofactor state, these proteins have little, if any procoagulant activity and do not participate to any significant degree in their respective macromolecular enzymatic complexes. Thrombin is considered a key physiological activator, cleaving select peptide bonds in FV and FVIII which ultimately leads to appropriate structural changes that impart cofactor function. As the active cofactors (FVa and FVIIIa) have an enormous impact on thrombin and FXa generation, maintaining FV and FVIII as inactive procofactors undoubtedly plays an important regulatory role that has likely evolved to maintain normal hemostasis. Over the past three decades there has been widespread interest in studying the proteolytic events that lead to the activation of these proteins. While a great deal has been learned, mechanistic explanations as to how bond cleavage facilitates conversion to the active cofactor species remain incompletely understood. However, recent advances have been made detailing how thrombin recognizes FV and FVIII and also how the FV B-domain plays a dominant role in maintaining the procofactor state. Here we review our current understanding of the molecular process of procofactor activation with a particular emphasis on FV.
Collapse
Affiliation(s)
- R M Camire
- Department of Pediatrics, Division of Hematology, The Children's Hospital of Philadelphia and The University of Pennsylvania, School of Medicine, Philadelphia, PA, USA.
| | | |
Collapse
|
9
|
Venom factor V from the common brown snake escapes hemostatic regulation through procoagulant adaptations. Blood 2009; 114:686-92. [PMID: 19365080 DOI: 10.1182/blood-2009-02-202663] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Venomous snakes produce an array of toxic compounds, including procoagulants to defend themselves and incapacitate prey. The Australian snake Pseudonaja textilis has a venom-derived prothrombin activator homologous to coagulation factors V (FV) and Xa (FXa). Here we show that the FV component (pt-FV) has unique biologic properties that subvert the normal regulatory restraints intended to restrict an unregulated procoagulant response. Unlike human FV, recombinant pt-FV is constitutively active and does not require proteolytic processing to function. Sequence comparisons show that it has shed a large portion of the central B-domain, including residues that stabilize the inactive procofactor state. Remarkably, pt-FV functions in the absence of anionic membranes as it binds snake-FXa with high affinity in solution. Furthermore, despite cleavage in the heavy chain, pt-FV is functionally resistant to activated protein C, an anticoagulant. We speculate this stability is the result of noncovalent interactions and/or a unique disulfide bond in pt-FV linking the heavy and light chains. Taken together, these findings provide a biochemical rationale for the strong procoagulant nature of venom prothrombinase. Furthermore, they illustrate how regulatory mechanisms designed to limit the hemostatic response can be uncoupled to provide a sustained, disseminated procoagulant stimulus for use as a biologic toxin.
Collapse
|
10
|
Kern L, Ignjatovic V, Winkel K, Summerhayes R, Monagle P. The differences of platelet response to snake venoms: A comparative study of children and adults. Toxicon 2008; 52:960-3. [DOI: 10.1016/j.toxicon.2008.09.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2007] [Revised: 09/10/2008] [Accepted: 09/19/2008] [Indexed: 11/26/2022]
|