Mounir S, Talbot P J
Virology Research Center, Institut Armand-Frappier, Université du Québec, Laval, Canada.
J Gen Virol. 1992 Oct;73 ( Pt 10):2731-6. doi: 10.1099/0022-1317-73-10-2731.
The gene encoding the membrane (M) protein of the OC43 strain of human coronavirus (HCV-OC43) was amplified by a reverse transcription-polymerase chain reaction of viral RNA with HCV-OC43- and bovine coronavirus (BCV)-specific primers. The nucleotide sequence of the cloned 1.5 kb fragment revealed an open reading frame (ORF) of 690 nucleotides which was identified as the M protein gene from its homology to BCV. This ORF encodes a protein of 230 amino acids with an M(r) of 26416. The gene is preceded by the motif UCCAAAC, analogous to the consensus coronavirus transcription initiation sequence. The M protein of HCV-OC43 shows features typical of all coronavirus M proteins studied: a hydrophilic, presumably external N terminus including about 10% of the protein, and a potential N-glycosylation site followed by three major hydrophobic transmembrane domains. The amino acid sequence of the M protein of HCV-OC43 has 94% identity with that of the Mebus strain of BCV, and also contains six potential O-glycosylation sites in the exposed N-terminal domain. Indeed, the glycosylation of the M protein was not inhibited in the presence of tunicamycin, which is indicative of O-glycosylation, as previously reported for BCV and murine hepatitis virus. Virions released from tunicamycin-treated cells contained the M glycoprotein but were devoid of both peplomer (S) and haemagglutinin-esterase (HE) proteins. Thus, inhibition of the N-glycosylation of the S and HE structural proteins prevented their incorporation into progeny virions, an indication that they are dispensable for virion morphogenesis, unlike the M protein.
通过使用人冠状病毒OC43株（HCV-OC43）特异性引物和牛冠状病毒（BCV）特异性引物对病毒RNA进行逆转录聚合酶链反应，扩增了编码人冠状病毒OC43株（HCV-OC43）膜（M）蛋白的基因。克隆的1.5 kb片段的核苷酸序列显示有一个690个核苷酸的开放阅读框（ORF），根据其与BCV的同源性确定为M蛋白基因。该ORF编码一个230个氨基酸的蛋白质，分子量为26416。该基因之前有UCCAAAC基序，类似于冠状病毒转录起始序列的共有序列。HCV-OC43的M蛋白具有所有已研究的冠状病毒M蛋白的典型特征：一个亲水的、可能位于外部的N端，约占该蛋白的10%，随后是一个潜在的N-糖基化位点，接着是三个主要的疏水跨膜结构域。HCV-OC43的M蛋白氨基酸序列与BCV的Mebus株有94%的同一性，并且在暴露的N端结构域还含有六个潜在的O-糖基化位点。事实上，衣霉素存在时M蛋白的糖基化并未受到抑制，这表明是O-糖基化，正如先前对BCV和鼠肝炎病毒的报道。从衣霉素处理的细胞中释放的病毒粒子含有M糖蛋白，但缺乏刺突（S）蛋白和血凝素酯酶（HE）蛋白。因此，S和HE结构蛋白的N-糖基化受到抑制阻止了它们掺入子代病毒粒子，这表明与M蛋白不同，它们对于病毒粒子形态发生是可有可无的。
