@entity1 pancreatic ribonuclease (HPR), a member of RNase A superfamily, has a high activity on double stranded (ds) RNA. By virtue of this activity HPR appears to be involved in the host-defense against pathogenic viruses. To delineate the mechanism of dsRNA cleavage by HPR, we have investigated the role of @entity1160 28 and @entity369 39 of HPR in its activity on dsRNA. A non-basic residue @entity2228 38, earlier shown to be important for dsRNA cleavage by HPR was also included in the study in the context of @entity1160 28 and @entity369 39. Nine variants of HPR respectively containing @entity70203 , @entity70204 , @entity70205 , @entity69314 , @entity70203 / @entity70205 , @entity70204 / @entity70205 , @entity70203 / @entity69314 , @entity70205 / @entity69314 and @entity70203 / @entity69314 / @entity70205 mutations were generated and functionally characterized. The far-UV CD-spectral analysis revealed all variants, except @entity70205 , to have structures similar to that of HPR. The catalytic activity of all HPR variants on single stranded RNA substrate was similar to that of HPR, whereas on dsRNA, the catalytic efficiency of all single residue variants, except for the @entity70204 , was significantly reduced. The dsRNA cleavage activity of @entity70205 / @entity69314 and @entity70203 / @entity69314 / @entity70205 variants was most drastically reduced to 4% of that of HPR. The variants having reduced dsRNA cleavage activity also had reduction in their dsDNA melting activity and thermal stability. Our results indicate that in HPR both @entity1160 28 and @entity369 39 are important for the cleavage of dsRNA. Although these residues are not directly involved in catalysis, both @entity369 39 and @entity1160 28 appear to be facilitating a productive substrate-enzyme interaction during the dsRNA cleavage by HPR.

Functional role of @entity1160 28 and @entity369 39 in double stranded RNA cleavage by XXXX pancreatic ribonuclease.

@entity1 :: ('9606', 'Species') :: ['Human'] @entity70204 :: ('p|SUB|Q|28|L', 'ProteinMutation') :: ['Q28L'] @entity70205 :: ('p|SUB|R|39|A', 'ProteinMutation') :: ['R39A'] @entity2228 :: ('CHEBI:57305', 'Chemical') :: ['glycine'] @entity1160 :: ('CHEBI:28300', 'Chemical') :: ['glutamine'] @entity69314 :: ('p|SUB|G|38|D', 'ProteinMutation') :: ['G38D'] @entity70203 :: ('p|SUB|Q|28|A', 'ProteinMutation') :: ['Q28A'] @entity369 :: ('CHEBI:29016', 'Chemical') :: ['arginine']
@entity1 :: (9606,Species) :: ['human']
