Nucleotide Sequence Coding for the N-Terminal Region of the Matrix Protein of Influenza Virus

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Abstract
After polyadenylation in vitro of the influenza virus RNA segment which contains the coding information for the matrix protein, a c[complementary]DNA copy can be made using the primer p(dT)8-da and reverse transcriptase. The sequence of 166 nucleotides of the cDNA was determined by a modification of the plus/minus method and adaptation of the dideoxy method for sequencing DNA. The cDNA sequence is of the same sense as the mRNA for matrix protein and contains a potential initiating codon, d(ATG), at position 26-28. When matrix protein purified from virus particles was digested with chymotrypsin or trypsin and the amino acid compositions of separated peptides determined, 1 peptide containing 9 amino acids was found which had a composition corresponding to that predicted by the cDNA sequence following the 1st methionine codon, confirming that protein synthesis initiates at this position. The compositions of 4 other peptides matched those predicted from the nucleotide sequence. There is no processing of the N [amino] terminus of the protein before incorporation into the virus particle except for removal of the N-terminal methionine and addition of a blocking group on the resulting N-terminal serine residue.