Molecular cloning and sequence analysis of the porcine transmissible gastroenteritis coronavirus matrix and peplomer protein genes

The porcine transmissible gastroenteritis coronavirus (TGEV) is a major cause of acute gastroenteritis in pigs and serves as an important model for coronavirus-induced gastroenteritis in other animals including humans. In order to understand the mechanisms of viral pathogensis and develop a possible recombinant vaccine, the genome of TGEV was molecularly cloned and genes for two of the three major viral structural proteins, the matrix protein and the peplomer protein, were studied in detail.

A copy DNA library was prepared from viral genomic RNA by using an oligodeoxynucleotide primer that is complementary to intergenic regions throughout the 20 kilobase genome. One hundred and thirteen clones were obtained and 64 were found to map within the 3' terminal 12 kilobases. Twelve clones were mapped at the region between 1.5 Kb and 8.5 Kb from 3' end of the TGEV genome and were sequenced in part by the chemical method. Two genes for the matrix and peplomer protein were found within this sequence.

The deduced amino acid sequence for the matrix protein is 262 amino acids long giving the protein a molecular weight of 29,544. The matrix protein is unusual among coronavirus matrix proteins in that it has a hydrophobic amino terminal signal peptide of 17 amino acids in addition to 3 internal hydrophobic domains that apparently also serve as signals for membrane translocation.

The deduced amino acid sequence for the peplomer protein is 1,447 amino acids long giving the protein a molecular weight of 160,345. The peplomer protein has an N-terminal signal peptide, a 19 amino acid transmembrane anchor region beginning 58 residues from its C-terminus, and 32 potential N-glycosylation sites throughout the molecule.

The peplomer protein gene was subcloned into the vaccinia virus vector in preparation for its use as vector to study its biological functions and as an experimental vaccine.