NAD+-dependent RNA terminal 2' and 3' phosphomonoesterase activity of a subset of Tpt1 enzymes.
RNA
; 25(7): 783-792, 2019 07.
Article
in En
| MEDLINE
| ID: mdl-31019096
ABSTRACT
The enzyme Tpt1 removes the 2'-PO4 at the splice junction generated by fungal tRNA ligase; it does so via a two-step reaction in which (i) the internal RNA 2'-PO4 attacks NAD+ to form an RNA-2'-phospho-ADP-ribosyl intermediate; and (ii) transesterification of the ribose O2â³ to the 2'-phosphodiester yields 2'-OH RNA and ADP-ribose-1â³,2â³-cyclic phosphate products. The role that Tpt1 enzymes play in taxa that have no fungal-type RNA ligase remains obscure. An attractive prospect is that Tpt1 enzymes might catalyze reactions other than internal RNA 2'-PO4 removal, via their unique NAD+-dependent transferase mechanism. This study extends the repertoire of the Tpt1 enzyme family to include the NAD+-dependent conversion of RNA terminal 2' and 3' monophosphate ends to 2'-OH and 3'-OH ends, respectively. The salient finding is that different Tpt1 enzymes vary in their capacity and positional specificity for terminal phosphate removal. Clostridium thermocellum and Aeropyrum pernix Tpt1 proteins are active on 2'-PO4 and 3'-PO4 ends, with a 2.4- to 2.6-fold kinetic preference for the 2'-PO4 The accumulation of a terminal 3'-phospho-ADP-ribosylated RNA intermediate during the 3'-phosphotransferase reaction suggests that the geometry of the 3'-p-ADPR adduct is not optimal for the ensuing transesterification step. Chaetomium thermophilum Tpt1 acts specifically on a terminal 2'-PO4 end and not with a 3'-PO4 In contrast, Runella slithyformis Tpt1 and human Tpt1 are ineffective in removing either a 2'-PO4 or 3'-PO4 end.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Phosphates
/
RNA
/
Phosphotransferases (Alcohol Group Acceptor)
/
Aeropyrum
/
Clostridium thermocellum
/
NAD
Limits:
Humans
Language:
En
Journal:
RNA
Journal subject:
BIOLOGIA MOLECULAR
Year:
2019
Document type:
Article
Affiliation country:
United States