对来自腹泻犬粪样的犬冠状病毒(CCV)南京株NJ17株及参考株171的M基因进行了克隆、测序,并与GenBank中所有已知CCV毒株及同亚群的猪冠状病毒(TGEV)和猫冠状病毒(FCoV)代表株的M基因进行了同源性比较和系统进化分析,同时对M蛋白的结构和功能进行了预测分析。结果表明,CCV171与近年在中国分离到的CCV毒株V1、V2及大熊猫源的毒株具有98.9%～99.5%的同源性,说明这些毒株可能是来自同一毒株的准种。NJ17与其他中国分离株及国外分离株的同源性为87.0%～91.9%,显示国内可能存在一个相对独立进化的CCV毒株。序列比较发现,所有CCV毒株在可能的同源重组“热点”区内都有一个CTTTAG序列,与鸡传染性支气管炎病毒同源重组模板交换位点附近的特征序列相似。CCVNJ17株M蛋白在N端50氨基酸序列与FCoV791683同源性高,而在后212氨基酸序列与TGEV同源性高,提示该毒株可能在M基因上曾经发生过不同病毒的同源重组。CCVM蛋白的结构及功能预测表明,所有毒株都具有分泌型信号肽,有4个螺旋跨膜区,N末端和C末端均位于膜内。M蛋白的两末端具有较强的抗原性,M蛋白上存在多种功能性氨基酸修饰位点且相对保守。N末端的氨基酸变异很大,但是功能性修饰位点相对保守,提示N末端的功能可能与构象有关。

Two M gene sequences of Canine coronavirus (CCV), from a wild strain NJ17 from a diarrhea dog faecal sample in Nanjing City and CCV 1-71 reference strain, were cloned and sequenced. The results showed, CCV 1-71 shared high similarity (98.9~99.5%) to CCV V1, V2 and a CCV strain from giant panda isolated in China 2003. It suggested that the above CCV strains existed quasispecies from a same ancestor strain. On M gene, CCV NJ17 shared 87.0~91.9% identities with other CCV strains and typical strains of Transmissible gastroenteritis virus (TGEV) of swine, and Feline coronaviruses (FCoVs) in the GenBank. The CCV NJ17 might be a separated evolutionary strain in China. Recombination mark sequences of all the landed strains on the M gene putative recombination region had a “CTTTAG” nucleotides , meeting to “CTT(A/T)(A/T)G” that always appeared near to the recombination “hot spot” in Infectious bronchitis virus RNA genome. The first 50 amino acid residues on N terminal of CCV NJ17 M protein was higher similar to FCoV 7