Protection of satellite tobacco necrosis virus ribonucleic acid by wheat germ 40S and 80S ribosomes.

Wheat germ ribosomes combine with the AUG codon at positions 30-32 from the 5' terminus of in vitro radioiodinated satellite tobacco necrosis virus (STNV) ribonucleic acid (RNA) to form initiation complexes that protect specific regions of the RNA from attack by ribonucleases. Wheat gern 80S ribosomes convey partial protection to a region 20-52 nucleotides from the 5' terminus of STNV RNA and convey protection against high levels of ribonucleases to a region 20-44 nucleotides from the 5' terminus of STNV RNA. Wheat germ 40S ribosomes convey partial protection to a region 3-52 nucleotides from the 5' terminus of STNV RNA and convey protection against high levels of ribonucleases to a region 10-47 nucleotides from the 5' terminum of STNV RNA. Characterization of these levels of protection against attack by specific ribonucleases establishes that wheat germ 40S and 80S ribosomes form initiation complexes with a linear conformation of STNV RNA lacking the 5'-terminal stem and loop anticipated by Leung and co-workers [Leung, D. W., Browning, K. S., Heckman, J. E., RajBhandary, U. L., & Clark, J. M., Jr. (1979) Biochemistry 18, 1361-1366] for the 5' terminus of STNV RNA.