Function
The alternative to using the RNA-guided mechanism for pseudouridine formation is a guide-independent mechanism acting through stand-alone enzymes. In eukaryotes, these enzymes are called Pus enzymes (Pseudouridine synthases), and they modify uridine by recognizing sequence and/or secondary structural elements of the RNA containing the target uridine.
pseudouridine synthase (PUS) catalyzes the conversion of uridine to tRNA pseudouridine in several types of RNA molecules[1], [2]. tRNAs are well-characterized as targets of these protein-only pseudouridine synthases, but recently have even been found to act on messenger RNAs in a variety of eukaryotic organisms, including humans[3], [4], [5]. In eubacteria PUS are active in the ribosomal large subunit Ribosomal large subunit pseudouridine synthase and in the ribosomal small subunit Ribosomal small subunit pseudouridine synthase.
Ribosomal large subunit pseudouridine synthases:
- RluA is responsible for synthesis of pseudouridine from uracil in positions 746 in 23S ribosomal RNA and in the anticodon loop of tRNAPhe, tRNACys and tRNALeu[6].
- RluB is responsible for synthesis of pseudouridine from uracil in position 2605 in 23S ribosomal RNA[7].
- RluC is responsible for synthesis of pseudouridine from uracil in positions 955, 2504 and 2580 in 23S ribosomal RNA[8].
- RluD is responsible for synthesis of pseudouridine from uracil in positions 1911, 1915 and 1917 in 23S ribosomal RNA[9].
- RluE is responsible for synthesis of pseudouridine from uracil in position 2457 in 23S ribosomal RNA[10].
- RluF is responsible for synthesis of pseudouridine from uracil in position 2604 in 23S ribosomal RNA[11].
Ribosomal small subunit pseudouridine synthase RsuA is responsible for synthesis of pseudouridine from uracil in positions 516 in 16S ribosomal RNA[12].
Structural highlights
The conversion of uridine to pseudouridine causes conformational change of PUS[13]. (1ze2).
