THE RLUC GENE OF ESCHERICHIA-COLI CODES FOR A PSEUDOURIDINE SYNTHASE THAT IS SOLELY RESPONSIBLE FOR SYNTHESIS OF PSEUDOURIDINE AT POSITION-955, POSITION-2504, AND POSITION-2580 IN 23-S RIBOSOMAL-RNA

Escherichia coli ribosomal RNA contains 10 pseudouridines, one in the 16 S RNA and nine in the 23 S RNA. Previously, the gene for the syntha se responsible for the 16 S RNA pseudouridine was identified and clone d, as was a gene for a synthase that makes a single pseudouridine in 2 3 S RNA. The yceC open reading frame of E. coil is one of a set of gen es homologous to these previously identified ribosomal RNA pseudouridi ne synthases. In this work, the gene was cloned, overexpressed, and sh own to code for a pseudouridine synthase able to react with in vitro t ranscripts of 23 S ribosomal RNA. Deletion of the gene and analysis of the 23 S RNA from the deletion strain for the presence of pseudouridi ne at its nine known sites revealed that this synthase is solely respo nsible in Dice for the synthesis of three of the nine pseudouridine re sidues, at positions 955, 2504, and 2580, Therefore, this gene has bee n renamed rluC. Despite the absence of one-third of the normal complem ent of pseudouridines, there was no change in the exponential growth r ate in either LB or M-9 medium at temperatures ranging from 24 to 42 d egrees C. From this work and our previous studies, we have now identif ied three synthases that account for 50% of the pseudouridines in the E, coli ribosome.