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近日,科學家對於武肺病毒的來源再有進一步的推論,其報告刊登在Cell Press的Current Biology裡頭(Impact Factor:9.19)。756Please respect copyright.PENANAQgg4OA49Bm
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Source: https://www.cell.com/current-biology/pdf/S0960-9822(20)30662-X.pdf756Please respect copyright.PENANAwHGG2hHIm6
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在2019年五至十月的雲南蝙蝠樣本中,中國科學家尋覓出一隻命名為RmYN02的冠狀病毒樣本。756Please respect copyright.PENANADiJEr8rg4Y
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1A)它的整體基因排組與武肺的相似度高達93.3%(依然不及於13年所找到的蝙蝠冠狀病毒RaTG13,96.1%),而Spike Protein的RBD氨基酸排組則只有62.4%的相似度。756Please respect copyright.PENANA2Y5hdoqNT9
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1B) 重溫一下,武肺的表面佈滿S protein(圖中藍色長方形),當S protein與人類細胞表面上的ACE2蛋白質結合的話,武肺就能成功進入人體體內搞事。756Please respect copyright.PENANA1yv32RxGCq
而S protein與ACE2觸碰的區域,我們稱之為RBD (Receptor Binding Domain)。756Please respect copyright.PENANAmKbIrK2sTG
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1C) 雖然RmYN02的基因整體排組相似度以及RBD相似度均不及其他樣本為高,但佢擁有一樣眾多樣本中均沒能夠找到的特徵,就是圖中所指的Polybasic cleavage site。756Please respect copyright.PENANAMAvP8yS9c0
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Polybasic cleavage site位於 S protein裡頭,武肺的氨基酸排組為PRRA,其排組沒能與其他樣本(03年SARS、RaTG13、馬來穿山甲樣本及其他常見的冠狀病毒)吻合,一直被人用作當成為武肺係人造病毒的「理據」。756Please respect copyright.PENANA2E7b7zcsqi
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而在RmYN02樣本中,科學尋覓得到 PAA排組的Polybasic cleavage site。雖然沒法與武肺的PRRA排組完全吻合,但這是首次在野生動物樣本中找到與武肺高吻合度(93.3%)而帶有類近武肺Polybasic cleavage site的樣本,再一步推展出武肺從野生動物中推展而來的可能性。756Please respect copyright.PENANAgJHaYbvl9U
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只不過,一日沒能夠從野生動物中找出與武肺達99.9%相近的樣本,一日也沒能夠得以確認武肺是從野生動物而來。756Please respect copyright.PENANAfPZocf3Iy7
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針對這一點,中科研亦有初步打算,將暫時基因與武肺相似度最高的RaTG13冠狀病毒弱化版本注入在不同的動物裡頭,然後再觀察病毒有否演變成為武肺的可能。756Please respect copyright.PENANAmnVz99BDrz
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但此舉能否成功,亦為之相當成疑。