Alphavirus-like methyltransferase (MT) domain (IPR002588)

Short name: Alphavirus-like_MT_dom

Overlapping homologous superfamilies


Domain relationships



This domain is found at the N terminus of the non-structural poly-protein of Tymoviruses, it spans the RNA methyltransferase domain of the replicase large subunit, which is a RNA-dependent RNA polymerase active in viral RNA replication [PMID: 10364504] is found in a wide range of ssRNA viruses (Tymovirales), including Hordeivirus, Tobravirus, Tobamovirus, Bromovirus, Closterovirus and Calicivirus. The poly-protein is processed into the replicase small subunit, which is the methyltransferase active in RNA capping and a RNA helicase. Methyltransferase displays a cytoplasmic capping enzyme activity. This function is necessary since all viral RNAs are synthesized in the cytoplasm, and host capping enzymes are restricted to the nucleus. The helicase region probably, which is immediately adjacent to the methyltransferase domain exhibits NTPase and RNA unwinding activities.

This methyltransferase is involved in mRNA capping. Capping of mRNA enhances its stability. This usually occurs in the nucleus. Therefore, many viruses that replicate in the cytoplasm encode their own enzyme [PMID: 10364504]. This is a specific guanine-7-methyltransferase domain involved in viral mRNA cap synthesis. Specificity for guanine 7 position is shown by NMR in [PMID: 10559320] and in vivo role in cap synthesis [PMID: 10982322]. Based on secondary structure prediction, the basic fold is believed to be similar to the common AdoMet-dependent methyltransferase fold [PMID: 8985362]. A curious feature of this methyltransferase domain is that it together with flanking sequences seems to have guanylyltransferase activity coupled to the methyltransferase activity [PMID: 8985362]. The domain is found throughout the so-called Alphavirus superfamily, (including alphaviruses and several other groups). It forms the defining, unique feature of this superfamily [PMID: 1645151].

GO terms

Biological Process

GO:0006396 RNA processing
GO:0080009 mRNA methylation

Molecular Function

GO:0003723 RNA binding
GO:0008174 mRNA methyltransferase activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
PROSITE profiles