biostudies-otherUnknown8(11)Kurinov IVProtein science : a publication of the Protein Society2399-405https://www.ebi.ac.uk/biostudies/studies/S-EPMC2144192Pokeweed antiviral protein (PAP) is a ribosome-inactivating protein (RIP), which enzymatically removes a single adenine base from a conserved, surface exposed loop sequence of ribosomal rRNA. We now present unprecedented experimental evidence that PAP can release not only adenine but guanine as well from Escherichia coli rRNA, albeit at a rate 20 times slower than for adenine. We also report X-ray structure analysis and supporting modeling studies for the interactions of PAP with guanine. Our modeling studies indicated that PAP can accommodate a guanine base in the active site pocket without large conformational changes. This prediction was experimentally confirmed, since a guanine base was visible in the active site pocket of the crystal structure of the PAP-guanine complex.biostudies-otherPMC2144192Europe PMCVenkatachalam TKRajamohan FUckun FMKurinov IVfalseX-ray crystallographic analysis of the structural basis for the interaction of pokeweed antiviral protein with guanine residues of ribosomal RNA.Pokeweed antiviral protein (PAP) is a ribosome-inactivating protein (RIP), which enzymatically removes a single adenine base from a conserved, surface exposed loop sequence of ribosomal rRNA. We now present unprecedented experimental evidence that PAP can release not only adenine but guanine as well from Escherichia coli rRNA, albeit at a rate 20 times slower than for adenine. We also report X-ray structure analysis and supporting modeling studies for the interactions of PAP with guanine. Our modeling studies indicated that PAP can accommodate a guanine base in the active site pocket without large conformational changes. This prediction was experimentally confirmed, since a guanine base was visible in the active site pocket of the crystal structure of the PAP-guanine complex.1999-01-01T00:00:00Z1999 Nov2019-03-27T02:22:13Z2019-03-27T02:22:13ZS-EPMC21441921059554210.1110/ps.8.11.2399 1QCI1QCG