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The nucleotide sequence of an Escherichia coli operon containing genes for the tRNA(m1G)methyltransferase, the ribosomal proteins S16 and L19 and a 21‐K polypeptide.
Author(s) -
Byström A.S.,
Hjalmarsson K.J.,
Wikström P.M.,
Björk G.R.
Publication year - 1983
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1983.tb01519.x
Subject(s) - operon , ribosomal rna , ribosomal protein , transfer rna , escherichia coli , nucleic acid sequence , biology , ecori , microbiology and biotechnology , genetics , gene , 30s , ribosome , rna , restriction enzyme
The nucleotide sequence of a 4.6‐kb SalI‐EcoRI DNA fragment including the trmD operon, located at min 56 on the Escherichia coli K‐12 chromosome, has been determined. The trmD operon encodes four polypeptides: ribosomal protein S16 (rpsP), 21‐K polypeptide (unknown function), tRNA‐(m1G)methyltransferase (trmD) and ribosomal protein L19 (rplS), in that order. In addition, the 4.6‐kb DNA fragment encodes a 48‐K and a 16‐K polypeptide of unknown functions which are not part of the trmD operon. The mol. wt. of tRNA(m1G)methyltransferase determined from the DNA sequence is 28 424. The probable locations of promoter and terminator of the trmD operon are suggested. The translational start of the trmD gene was deduced from the known NH2‐terminal amino acid sequence of the purified enzyme. The intercistronic regions in the operon vary from 9 to 40 nucleotides, supporting the earlier conclusion that the four genes are co‐transcribed, starting at the major promoter in front of the rpsP gene. Since it is known that ribosomal proteins are present at 8000 molecules/genome and the tRNA‐(m1G)methyltransferase at only approximately 80 molecules/genome in a glucose minimal culture, some powerful regulatory device must exist in this operon to maintain this non‐coordinate expression. The codon usage of the two ribosomal protein genes is similar to that of other ribosomal protein genes, i.e., high preference for the most abundant tRNA isoaccepting species. The trmD gene has a codon usage typical for a protein made in low amount in accordance with the low number of tRNA‐(m1G)methyltransferase molecules found in the cell.