Kubo Yoshinao, Amanuma Hiroshi
Department of Preventive Medicine and AIDS Research, Institute of Tropical Medicine, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan.
Molecular Cell Science Laboratory, RIKEN (The Institute of Physical and Chemical Research), Hirosawa 2-1, Wako, Saitama 351-0198, Japan.
J Gen Virol. 2003 Aug;84(Pt 8):2253-2257. doi: 10.1099/vir.0.19126-0.
Moloney murine leukaemia virus (MoMLV) enters host cells by membrane fusion between the viral envelope and the host cell membrane. The cytoplasmic tail (R peptide) of the MoMLV envelope protein (Env) is cleaved by the viral protease during virion maturation. R peptide-truncated Env induces syncytia in susceptible cells but R peptide-containing Env does not, indicating that the R peptide inhibits membrane fusion. To examine the function of amino acid residues at the R peptide cleavage site in virus entry, mutant Env expression plasmids containing amino acid substitutions at these cleavage site residues were constructed. Some of these mutants induced syncytia in NIH 3T3 cells, even though they expressed the R peptide, indicating the importance of these residues for membrane fusion inhibition by the R peptide. Some mutants in which R peptide cleavage was detected had comparable transduction efficiency to wild-type Env, but mutants in which R peptide cleavage was not detected had lower transduction efficiency than wild-type Env. This result strongly supports that R peptide cleavage is required for virus entry.
莫洛尼鼠白血病病毒（MoMLV）通过病毒包膜与宿主细胞膜之间的膜融合进入宿主细胞。在病毒粒子成熟过程中，MoMLV包膜蛋白（Env）的细胞质尾巴（R肽）被病毒蛋白酶切割。R肽截短的Env在易感细胞中诱导形成多核巨细胞，但含R肽的Env则不会，这表明R肽抑制膜融合。为了研究R肽切割位点的氨基酸残基在病毒进入过程中的功能，构建了在这些切割位点残基处含有氨基酸取代的突变Env表达质粒。其中一些突变体在NIH 3T3细胞中诱导形成多核巨细胞，即使它们表达了R肽，这表明这些残基对于R肽抑制膜融合很重要。一些检测到R肽切割的突变体具有与野生型Env相当的转导效率，但未检测到R肽切割的突变体的转导效率低于野生型Env。这一结果有力地支持了病毒进入需要R肽切割。
