[Topography of ribosomal proteins: reconsideration of of protein map of small ribosomal subunit].

Exposure of proteins on the surface of the small (30S) ribosomal subunit of Escherichia coli was studied by the hot tritium bombardment technique. Eight of 21 proteins of the 30 S subunit (S3, S8, S10, S12, S15, S16, S17, and S19) had virtually no groups exposed on the surface of the particle, i.e., they were mainly hidden inside. Seven proteins (S1, S4, S5, S7, S18, S20, and S21) were all well exposed on the surface of the particle, thus being outside proteins. The remaining proteins (S2, S6, S9 and/or S11, S13, and S14) were partially exposed. On the basis of these results a reconcilement of the three-dimensional protein map of the small ribosomal subunit has been done and corrected model is proposed.