The large (L) protein subunit of unsegmented negative-strand RNA virus polymerases is thought to be responsible for the majority of enzymic activities involved in viral transcription and replication. In order to gain insight into this multifunctional role we compared the deduced amino acid sequences of five L proteins of rhabdoviruses (vesicular stomatitis virus and rabies virus) or paramyxoviruses (Sendai virus, Newcastle disease virus and measles virus). Statistical analysis showed that they share an atypical amino acid usage, outlining the uniqueness of the negative-strand virus life style. Similarity studies between L proteins traced evolutionary relationships in partial disagreement with the present taxonomic arrangement of this group of viruses. The five L proteins exhibit a high degree of homology along most of their length, with strongly invariant amino acids embedded in conserved blocks separated by variable regions, suggesting a structure of concatenated functional domains. The most highly conserved central block contains the probable active site for RNA synthesis. We tentatively identified some other functional sites, distributed around this central core, that would naturally work together to assure the polymerase activity. This provides detailed guidelines for the future study of L proteins by site-directed mutagenesis.


Article metrics loading...

Loading full text...

Full text loading...


Most cited this month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error