RESUMO
Antigenic mutants of poliovirus (Sabin strain, serotype 1) were isolated by the resistance of the virus to anti-Sabin neutralizing monoclonal antibodies. The amino acid replacements within the capsid protein sequence causing the altered antigenicity were identified for each of 63 isolates. The mutations cluster into distinct nonoverlapping peptide segments that group into three general immunological phenotypes on the basis of cross-neutralization analyses with 15 neutralizing anti-Sabin monoclonal antibodies. Location of the mutated amino acid residues within the three-dimensional structure of the virion indicates that the majority of these amino acid residues are highly exposed and located within prominent structural features of the viral surface. Those mutated amino acid residues that are less accessible to antibody interaction are often involved in hydrogen bonds or salt bridges that would stabilize the local tertiary structure of the antigenic site. The interactions of the peptide segments that form these neutralizing sites suggest specific models for the generation of neutralization-resistant variants and for the interaction between the viral surface and antibody.
Assuntos
Epitopos/análise , Poliovirus/imunologia , Anticorpos Monoclonais , Capsídeo/análise , Capsídeo/imunologia , Simulação por Computador , Humanos , Substâncias Macromoleculares , Modelos Moleculares , Mutação , Poliovirus/genética , Vacina Antipólio Oral/imunologia , Relação Estrutura-Atividade , Células Tumorais Cultivadas , Vírion/ultraestruturaRESUMO
The yeast genes that code for the serine-inserting SUP-RL1 amber and SUQ5 ochre suppressors have been cloned and sequenced. These two unlinked genes differ by only three base pairs in their coding regions yet they encode tRNAs of different translational specificities, and while the SUP-RL1 gene has a 19-base pair intervening sequence, the SUQ5 gene has none.
Assuntos
RNA de Transferência/genética , Saccharomyces cerevisiae/genética , Supressão Genética , Sequência de Bases , Clonagem Molecular , Enzimas de Restrição do DNA , Mutação , Hibridização de Ácido NucleicoRESUMO
The present communication describes the molecular cloning and DNA sequence determination of the rat growth hormone (rGH) gene. The rGH gene was cloned on an 11 kilobase EcoRI fragment of total rat DNA; it has four intervening sequences which correspond in position to those of the human growth hormone (hGH) gene. One of the intervening sequences in the rGH gene contains a possible transposable element: a 200 base pair direct repeat that is itself flanked by an exact 15 base pair direct repeat. The DNA sequence was used to estimate the location of the 5' end of the mature growth hormone mRNA. By S1 nuclease mapping it was located approximately 25 bases "downstream" from a TATAAA sequence presumed to play a role in initiation of transcription of the rGH gene.
Assuntos
DNA/genética , Hormônio do Crescimento/genética , RNA Mensageiro/genética , Animais , Sequência de Bases , Clonagem Molecular , Enzimas de Restrição do DNA , Hibridização de Ácido Nucleico , Capuzes de RNA/genética , Ratos , Transcrição GênicaRESUMO
Purified, isolated yeast tRNA Ser2 was used as a hybridization probe to estimate the number of tRNA Ser2 genes in the yeast genome. Molecular clones of several of the genes were obtained. Three examples were studied in detail with respect to their genomic organization, and DNA sequences were determined for them. There appear to be eleven tRNA Ser2 genes in the yeast genome. They are neither tandemly repeated, nor clustered with other tRNA genes. They contain no intervening sequences.
