Supplementary Material for: Genetic Variability and Sequence Relatedness of Matrix Protein in Viruses of the Families Paramyxoviridae and Pneumoviridae

<b><i>Background:</i></b> The families Paramyxoviridae and Pneumoviridae comprise a broad spectrum of viral pathogens that affect human health. The matrix (M) protein of these viruses has a central role in their life cycle. In line with this, molecular characteristics of the M proteins from variable viruses that circulated in Croatia were investigated. <b><i>Methods:</i></b> Sequences of the M proteins of human parainfluenza virus (HPIV) 1–3 within the family Paramyxoviridae, human metapneumovirus (HMPV), and human respiratory syncytial virus from the family Pneumoviridae<i></i> were obtained and analyzed. <b><i>Results:</i></b> M proteins were very diverse among HPIVs, but highly conserved within each virus. More variability was seen in nucleotide sequences of M proteins from the Pneumoviridae<i></i> family. An insertion of 8 nucleotides in the 3′ untranslated region in 1 HMPV M gene sequence was discovered (HR347-12). As there are no samples with such an insertion in the database, this insertion is of interest and requires further research. <b><i>Conclusion:</i></b> While we have confirmed that M proteins were conserved among individual viruses, any changes that are observed should be given attention and further researched. Of special interest is inclusion of HPIV2 M proteins in this analysis, as these proteins have not been studied to the same extent as other paramyxoviruses.