Evidence that a single EF-Ts suffices for the recycling of multiple and divergent EF-Tu species in Streptomyces coelicolor A3(2) and Streptomyces ramocissimus.
The tsf genes from Streptomyces coelicolor A3(2) and Streptomyces ramocissimus, encoding the guanine-nucleotide exchange factor EF-Ts, were cloned and sequenced. Streptomycetes have multiple and highly divergent EF-Tu species, with EF-Tu1 and EF-Tu3 showing only about 65% amino acid sequence identity, and yet these can apparently interact with a single EF-Ts species. tsf lies in an operon with rpsB, which encodes ribosomal protein S2. The amino acid sequence of S2 from S. coelicolor differs from most other bacterial S2 homologues in having a C-terminal extension of 70 aa residues with a highly repetitive organization, the function of which is unknown. Transcription analysis of the rpsB-tsf operon of S. coelicolor by promoter probing, nuclease S1 mapping and Northern blotting revealed that the genes give rise to a bicistronic transcript from a single promoter upstream of rpsB. An attenuator was identified in the rpsB-tsf intergenic region; it results in an approximately 2:1 ratio of rpsB vs tsf transcripts. Although tuf1, encoding the major EF-Tu, is located in the rpsL ribosomal protein operon, an additional promoter in the fus-tuf1 intergenic region leads to a significant excess of EF-Tu over ribosomes. Most amino acid residues known from the Escherichia coli crystal structure of the EF-Tu-EF-Ts complex to be directly involved in interaction between the two elongation factors are conserved between E. coli and Streptomyces. However, whenever interaction residues in the EF-Tu moiety show divergence among Streptomyces EF-Tu1, EF-Tu2 and EF-Tu3, the single Streptomyces EF-Ts exhibits compensatory substitutions of the corresponding residues. These apparently enable productive interaction to occur with all three EF-Tus.
Hoogvliet
Gertjan
G
Department of Biochemistry, Leiden Institute of Chemistry, Leiden University, PO Box 9502, 2300 RA Leiden, The Netherlands1.
van Wezel
Gilles P
GP
Department of Biochemistry, Leiden Institute of Chemistry, Leiden University, PO Box 9502, 2300 RA Leiden, The Netherlands1.
Kraal
Barend
B
Department of Biochemistry, Leiden Institute of Chemistry, Leiden University, PO Box 9502, 2300 RA Leiden, The Netherlands1.
D000595:Amino Acid Sequence; D001483:Base Sequence; D015139:Blotting, Southern; D003001:Cloning, Molecular; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D005810:Multigene Family; D009876:Operon / Q000235:genetics; D010444:Peptide Elongation Factor Tu / Q000235:genetics / Q000378:metabolism*; D010445:Peptide Elongation Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D015183:Restriction Mapping; D000091243:Ribosomal Protein S9; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013302:Streptomyces / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
D029968:Escherichia coli Proteins; D010445:Peptide Elongation Factors; D000091243:Ribosomal Protein S9; D012269:Ribosomal Proteins; C000717190:RpsI protein, E coli; C023512:elongation factor Ts; C030004:ribosomal protein S2; D010444:Peptide Elongation Factor Tu