STRUCT CHAR OF PROTEIN NUCLEIC ACID COMPLEXES IN NUCLEAR IMPORT

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Nuclear import of proteins and nucleic acids is central to many cellular processes and cell-pathogen interactions. Some bacteria and viruses encode specialized proteins that Mansport genomic, DNA and RNA molecules of the invading pathogen into the host cell nucleus. One of these is the VirE2 protein of Agrobacterium. Agrobactenwn elicits neoplastic growths on many plant species by taiisporting a single-stranded copy of the bacterial tranderred DNA (T-DNA) into the. plant cell nucleus. VirE2 alone appears to be sufficient to transport T-DNA into the host cell nucleus. Since the T-DNA is not sequence specific, the complex between any ssDNA and VirE2 is competent for active nuclear imporL M 13 ssDNA and VirE2 were incubated and examined in the STEM. Both freeze-dried and negatively stained specimens were prepared. The rather rigid uniform filaments were analyzed, including mass/length, radial density profile analyses, and modeling to fit the observed stained data. A model of a hollow phone-cord like coil, 12.6 nin in diameter, with a helical pitch of 4.4 nrn, and approximately one VirE2 per twenty bases, fits all the data. TMV movement protein is not part of the TMV virion but is reponsible for the ftwisport into the host. Complexes of the protein and the TMV RNA were examined in the STEK but the protein/RNA ratio was too low. Further work is planned