| Type: | Domain | Name: | Peptidase A3A, cauliflower mosaic virus |
| Description: | Aspartic endopeptidases of vertebrate, fungal and retroviral origin have been characterised []. More recently, aspartic endopeptidases associated with the processing of bacterial type 4 prepilin [] and archaean preflagellin have been described [, ].Structurally, aspartic endopeptidases are bilobal enzymes, each lobe contributing a catalytic Asp residue, with an extended active site cleft localised between the two lobes of the molecule. One lobe has probably evolved from the other through a gene duplication event in the distant past. In modern-day enzymes, although the three-dimensional structures are very similar, the amino acid sequences are more divergent, except for the catalytic site motif, which is very conserved. The presence and position of disulphide bridges are other conserved features of aspartic peptidases. All or most aspartate peptidases are endopeptidases. These enzymes have been assigned into clans (proteins which are evolutionary related), and further sub-divided into families, largely on the basis of their tertiary structure.This group of sequences contain an aspartic peptidase signature that belongs to MEROPS peptidase family A3, subfamily A3A (cauliflower mosaic virus-type endopeptidase, clan AA). Cauliflower mosaic virusbelongs to the Retro-transcribing viruses, which have a double-stranded DNA genome. The genome includes an open reading frame (ORF V) that shows similarities to the polgene of retroviruses. This ORF codes for a polyprotein that includes a reverse transcriptase, which, on the basis of a DTG triplet near the N terminus, was suggested to include an aspartic protease. The presence of an asparticprotease has been confirmed by mutational studies, implicating Asp-45 in catalysis. The protease releases itself from the polyprotein and is involved in reactions required to process the ORF IV polyprotein, which includes theviral coat protein []. The viral aspartic peptidase signature has also been found associated with a polyprotein encoded by integrated pararetrovirus-like sequences in the genome of Nicotiana tabacum(Common tobacco) []. | Short Name: | Pept_A3A |
