Structure of functionally activated small ribosomal subunit at 3.3 angstrom resolution

The small ribosomal subunit performs the decoding of genetic information du ring translation. The structure of that from Thermus thermophilus shows tha t the decoding center, which positions mRNA and three tRNAs, is constructed entirely of RNA. The entrance to the mRNA channel will encircle the messag e when a latch-like contact closes and contributes to processivity and fide lity. Extended RNA helical elements that run longitudinally through the bod y transmit structural changes, correlating events at the particle's far end with the cycle of mRNA translocation at the decoding region. 96% of the nu cleotides were traced and the main fold of all proteins was determined. The latter are either peripheral or appear to serve as linkers. Some may assis t the directionality of translocation.