Luo Z L, Weiss S R
Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia 19104, USA.
Adv Exp Med Biol. 1998;440:17-23. doi: 10.1007/978-1-4615-5331-1_3.
The coronavirus peplomer protein S is responsible for attachment and fusion during viral entry as well as for the induction of cell to cell fusion. While several regions within S have been shown to influence the ability to induce fusion, the region of the protein actually responsible for fusion, the fusion peptide, has not yet been identified. We identified two hydrophobic peptides (peptides #1 and #2) within MHV-A59 S2 as possible fusion domains. This was based on hydrophobicity, conservation among coronavirus S proteins and the prediction of a sided helix conformation. Using site directed mutagenesis and an in vitro cell to cell fusion assay we showed that substitution of hydrophobic amino acids with charged amino acids, within the predicted hydrophobic face of either of these two peptides eliminated fusion. Within peptide #1 substitution of the same hydrophobic amino acids with other hydrophobic amino acids or substitution of polar amino acids with charged or polar amino acids had little effect on fusion. Thus peptides #1 and #2 remain likely candidates for the MHV fusion peptide. A third previously identified peptide within S2 (Chambers et al., 1990) is unlikely as a fusion peptide as it is not well conserved among coronaviruses and substitution within the hydrophobic face with charged amino acids does not effect fusion.
冠状病毒纤突蛋白S负责病毒进入过程中的附着与融合以及细胞间融合的诱导。虽然已证明S蛋白内的几个区域会影响诱导融合的能力，但该蛋白中实际负责融合的区域，即融合肽，尚未确定。我们在MHV - A59 S2内鉴定出两个疏水肽（肽#1和肽#2）作为可能的融合结构域。这是基于疏水性、冠状病毒S蛋白之间的保守性以及对单侧螺旋构象的预测。使用定点诱变和体外细胞间融合试验，我们发现，在这两个肽中任一个的预测疏水面上，用带电荷氨基酸取代疏水氨基酸会消除融合。在肽#1中，用其他疏水氨基酸取代相同的疏水氨基酸，或用带电荷或极性氨基酸取代极性氨基酸，对融合影响很小。因此，肽#1和肽#2仍是MHV融合肽的可能候选者。先前在S2中鉴定出的第三个肽（Chambers等人，1990年）不太可能是融合肽，因为它在冠状病毒中保守性不佳，并且在疏水面上用带电荷氨基酸取代不会影响融合。
