5btb | pdb_00005btb
Crystal Structure of Ashbya gossypii Rai1
Structural highlights
FunctionDXO_ASHGO Decapping enzyme for NAD-capped RNAs: specifically hydrolyzes the nicotinamide adenine dinucleotide (NAD) cap from a subset of RNAs by removing the entire NAD moiety from the 5'-end of an NAD-capped RNA (By similarity). The NAD-cap is present at the 5'-end of some RNAs and snoRNAs (By similarity). In contrast to the canonical 5'-end N7 methylguanosine (m7G) cap, the NAD cap promotes mRNA decay (By similarity). Also acts as a non-canonical decapping enzyme that removes the entire cap structure of m7G capped or incompletely capped RNAs and mediates their subsequent degradation (PubMed:26101253). Specifically degrades pre-mRNAs with a defective m7G cap and is part of a pre-mRNA capping quality control (PubMed:26101253). Has decapping activity toward incomplete 5'-end m7G cap mRNAs such as unmethylated 5'-end-capped RNA (cap0), while it has no activity toward 2'-O-ribose methylated m7G cap (cap1) (By similarity). Also has 5'-3' exonuclease activity (PubMed:26101253). Also possesses RNA 5'-pyrophosphohydrolase activity by hydrolyzing the 5'-end triphosphate to release pyrophosphates (PubMed:26101253).[UniProtKB:O13836][UniProtKB:O70348][UniProtKB:Q06349][1] Publication Abstract from PubMedRecent studies showed that Rai1 and its homologs are a crucial component of the mRNA 5'-end capping quality control mechanism. They can possess RNA 5'-end pyrophosphohydrolase (PPH), decapping, and 5'-3' exonuclease (toward 5' monophosphate RNA) activities, which help to degrade mRNAs with incomplete 5'-end capping. A single active site in the enzyme supports these apparently distinct activities. However, each Rai1 protein studied so far has a unique set of activities, and the molecular basis for these differences are not known. Here, we have characterized the highly diverse activity profiles of Rai1 homologs from a collection of fungal organisms and identified a new activity for these enzymes, 5'-end triphosphonucleotide hydrolase (TPH) instead of PPH activity. Crystal structures of two of these enzymes bound to RNA oligonucleotides reveal differences in the RNA binding modes. Structure-based mutations of these enzymes, changing residues that contact the RNA but are poorly conserved, have substantial effects on their activity, providing a framework to begin to understand the molecular basis for the different activity profiles. Structural and biochemical studies of the distinct activity profiles of Rai1 enzymes.,Wang VY, Jiao X, Kiledjian M, Tong L Nucleic Acids Res. 2015 Jun 22. pii: gkv620. PMID:26101253[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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