The primary structure of protein S14 from the small ribosomal subunit of Escherichia coli

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Abstract
Protein S14 was isolated in pure form from Escherichia coli ribosomal 30 S subunits. Its complete amino acid sequence was determined by a combination of various approaches, such as enzymatic and chemical cleavage of the protein chain, isolation of the resulting peptides as well as manual and automatic sequence determination by the Edman degradation technique. The protein has an M r of 11 191 and consists of 98 amino acid residues, 26 of which are basic and 9 acidic. One residue each of cysteine, histidine, tyrosine and tryptophan is present in the protein. The secondary structure of protein S14 as predicted according to 4 different programs shows a long α‐helix in the N‐terminal region and a short α‐helix near the C‐terminus of the protein chain. When the amino acid sequence of protein S14 was compared with that of all other E. coli ribosomal proteins with computer search programs, only relatively short homologous regions were found. A comparison between protein S14 of E. coli and the homologous protein from Bacillus stearothermophilus revealed ∼35% identity within the protein regions available for comparison.