title: On the role of protein S4 N-terminal residues 1 through 30 in 30S ribosome function.
abstract: 30S ribosomal protein S4 contains a single cysteine residue at position 31. We have selectively cleaved the peptide bond adjacent to this residue using the reagent 2-nitro-5-thiocyanobenzoic acid. The two resultant fragments were purified. The smaller S4-fragment (1-30) was found to be incapable of interacting with 16S RNA directly. This fragment also is not incorporated into a particle reconstituted from 16S RNA and 20 purified proteins with S4 missing. In contrast, the large S4-fragment (31-203) appears to be fully functional in ribosome assembly. Replacement of S4 with this fragment in the reconstitution reaction leads to a complete 30S ribosome containing all 30S proteins. This particle has a full capacity to bind poly U but has lost all activity for poly U directed phe-tRNA binding. We therefore propose that the N-terminus of protein S4 is not critical for ribosome assembly but is essential for tRNA binding.
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D004926:Escherichia coli / Q000648:ultrastructure; D010446:Peptide Fragments / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism; D012269:Ribosomal Proteins / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism* / Q000648:ultrastructure; D013329:Structure-Activity Relationship
chemical_list: D010446:Peptide Fragments; D012333:RNA, Messenger; D012346:RNA, Transfer, Amino Acyl; D012269:Ribosomal Proteins