scholarly journals Structure of the saxiphilin:saxitoxin (STX) complex reveals a convergent molecular recognition strategy for paralytic toxins

2019 ◽  
Vol 5 (6) ◽  
pp. eaax2650 ◽  
Author(s):  
Tien-Jui Yen ◽  
Marco Lolicato ◽  
Rhiannon Thomas-Tran ◽  
J. Du Bois ◽  
Daniel L. Minor

Dinoflagelates and cyanobacteria produce saxitoxin (STX), a lethal bis-guanidinium neurotoxin causing paralytic shellfish poisoning. A number of metazoans have soluble STX-binding proteins that may prevent STX intoxication. However, their STX molecular recognition mechanisms remain unknown. Here, we present structures of saxiphilin (Sxph), a bullfrog high-affinity STX-binding protein, alone and bound to STX. The structures reveal a novel high-affinity STX-binding site built from a “proto-pocket” on a transferrin scaffold that also bears thyroglobulin domain protease inhibitor repeats. Comparison of Sxph and voltage-gated sodium channel STX-binding sites reveals a convergent toxin recognition strategy comprising a largely rigid binding site where acidic side chains and a cation-π interaction engage STX. These studies reveal molecular rules for STX recognition, outline how a toxin-binding site can be built on a naïve scaffold, and open a path to developing protein sensors for environmental STX monitoring and new biologics for STX intoxication mitigation.




Sensors ◽  
2021 ◽  
Vol 21 (8) ◽  
pp. 2757
Author(s):  
W. Rudolf Seitz ◽  
Casey J. Grenier ◽  
John R. Csoros ◽  
Rongfang Yang ◽  
Tianyu Ren

This perspective presents an overview of approaches to the preparation of molecular recognition agents for chemical sensing. These approaches include chemical synthesis, using catalysts from biological systems, partitioning, aptamers, antibodies and molecularly imprinted polymers. The latter three approaches are general in that they can be applied with a large number of analytes, both proteins and smaller molecules like drugs and hormones. Aptamers and antibodies bind analytes rapidly while molecularly imprinted polymers bind much more slowly. Most molecularly imprinted polymers, formed by polymerizing in the presence of a template, contain a high level of covalent crosslinker that causes the polymer to form a separate phase. This results in a material that is rigid with low affinity for analyte and slow binding kinetics. Our approach to templating is to use predominantly or exclusively noncovalent crosslinks. This results in soluble templated polymers that bind analyte rapidly with high affinity. The biggest challenge of this approach is that the chains are tangled when the templated polymer is dissolved in water, blocking access to binding sites.



2014 ◽  
Vol 97 (2) ◽  
pp. 492-497 ◽  
Author(s):  
Andrew D Turner ◽  
Monika Dhanji-Rapkova ◽  
Clothilde Baker ◽  
Myriam Algoet

Abstract AOAC Official Method 2005.06 precolumn oxidation LC-fluorescence detection method has been used for many years for the detection and quantitation of paralytic shellfish poisoning (PSP) toxins in bivalve molluscs. After extensive single- and multiple-laboratory validation, the method has been slowly gaining acceptance worldwide as a useful and practical tool for official control testing. In Great Britain, the method has become routine since 2008, with no requirement since then for reverting back to the bioassay reference method. Although the method has been refined to be semiautomated, faster, and more reproducible, the quantitation step can be complex and time-consuming. An alternative approach was developed to utilize the qualitative screening results for generatinga semiquantitative results assessment. Data obtained over 5 years enabled the comparison of semiquantitative and fully quantitative PSP results in over 15 000 shellfish samples comprising eight different species showed that the semiquantitative approach resulted in over-estimated paralytic shellfish toxin levels by an average factor close to two in comparison with the fully quantified levels. No temporal trends were observed in the data or relating to species type, with the exception of surf clams. The comparison suggested a semiquantitative threshold of 800 μg saxitoxin (STX) eq/kg should provide a safe limitfor the determination of samples to be forwarded to full quantitation. However, the decision was taken to halve this limit to include an additional safety factor of 2, resulting in the use of a semiquantitative threshold of 400 μg STX eq/kg. Implementation of the semiquantitative method into routine testing would result in a significant reduction in the numbers of samples requiring quantitation and have a positive impact on the overall turnaround of reported PSP results. The refined method would be appropriate for any monitoring laboratory faced with high throughput requirements.





2014 ◽  
Vol 19 (1) ◽  
pp. 27
Author(s):  
Haryoto Kusnoputranto ◽  
Setyo S Moersidik ◽  
Djarot S Wisnubroto ◽  
Murdahayu Makmur

Ledakan mikroalga sering dilaporkan terjadi di Teluk Jakarta, dimana di lokasi tersebut juga terdapat kegiatan budidaya kerang hijau (Perna viridis). Terkait dengan hal tersebut maka dilakukan studi akumulasi dan depurasi toksin PSP (Paralytic Shellfish Poisoning) pada kerang hijau. Studi akumulasi dilakukan di bagan kerang hijau perairan Cilincing Jakarta Utara, dengan memisahkan kerang hijau yang berukuran sama dan ditempatkan kembali ke bagan. Sampling dilakukan setiap minggu selama 2 bulan dan diukur juga kelimpahan fitoplankton, pH, suhu dan salinitas perairan. Depurasi dilakukan di Unit Depurasi Kekerangan KKP Panimbang Banten, yang dilakukan selama 24 jam. Pencuplikan  sampel dilakukan setiap jam pada 4 jam pertama dan setiap 2 dan 3 jam pada waktu berikutnya. Penentuan konsentrasi toksin PSP dilakukan dengan menggunakan HPLC detektor fluoresensi. Prosedur preparasi, ekstraksi dan pengukuran konsentrasi toksin mengikuti Manual AOAC Official Method 2005.06 untuk toksin PSP dalam kekerangan. Akumulasi toksin PSP oleh kerang hijau di perairan Cilincing pada bulan Januari–Pebruari 2011 berkisar antara 4,11–11,96 µg STX eq. per 100 g dan tidak mempunyai korelasi dengan kelimpahan Dinoflagelata di perairan. Hal ini disebabkan uji akumulasi tidak dilakukan pada saat blooming mikroalga. Uji depurasi selama 24 jam mengeliminasi toksin PSP sebesar 60%, sehingga bisa diajukan sebagai sistem pemutus rantai toksin dari mikroalga ke manusia. Kata kunci: akumulasi, depurasi, PSP toksin, kerang hijau, Cilincing Microalgae blooms have been frequently reported in the Jakarta Bay, which is also the location of green mussel (Perna viridis) aquaculture. Accumulation and depuration of Paralytic Shellfish Poisoning (PSP) toxin in the green mussels were investigated in the field, where the toxin accumulation studies conducted in the mussel farming at Cilincing, North Jakarta. Accumulation test carried out by placing back the selected green mussel (equal size) into the mussel farming. Every week for 2 months, the green mussel were collected from mussel farming and transported to the laboratory. The fitoplankton abundance also was checked including pH, Suhue and salinitiy paramaters. Toxin depuration was conducted at Clams Sanitation Unit at Panimbang Banten. The depuration studies were conducted for 24 hours with sampling every hour in the first 4 hours and every 3 and 2 hours until the 24th hour. Preparation, extraction and toxin concentration measurements performed by following the Manual AOAC Official Method 2005.06 for PSP toxin in oyster. This research concluded that the accumulation of PSP toxin by green mussel, Perna viridis in the mussel farming at Cilincing, North Jakarta in ranged between 4,11–11,96 µg STX eq. per 100 g during January–February 2011. No correlation between PSP toxin concentration in the green mussel, Perna viridis with abundance of the PSP toxin sources phytoplankton, because the study wasnt done when microalgae blooming. The depuration processes was eliminate 60% the PSP toxins for 24 hours depuration processing. It can be proposes as a banded system the PSP toxin from algae to human being. Keywords: accumulation, depuration, PSP toxin, green mussel, Cilincing



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