3u1k
From Proteopedia
Crystal structure of human PNPase
Structural highlights
DiseasePNPT1_HUMAN Combined oxidative phosphorylation defect type 13;Autosomal recessive nonsyndromic sensorineural deafness type DFNB. Combined oxidative phosphorylation deficiency 13 (COXPD13) [MIM:614932: A mitochondrial disorder characterized by early onset severe encephalomyopathy, dystonia, choreoathetosis, bucofacial dyskinesias and combined mitochondrial respiratory chain deficiency. Nerve conductions velocities are decreased. Levels of plasma and cerebrospinal fluid lactate are increased. Note=The disease is caused by mutations affecting the gene represented in this entry. Deafness, autosomal recessive, 70 (DFNB70) [MIM:614934: A form of non-syndromic deafness characterized by severe, bilateral hearing impairment with prelingual onset, resulting in inability to acquire normal speech. Note=The disease is caused by mutations affecting the gene represented in this entry. FunctionPNPT1_HUMAN RNA-binding protein implicated in numerous RNA metabolic processes. Hydrolyzes single-stranded polyribonucleotides processively in the 3'-to-5' direction. Mitochondrial intermembrane factor with RNA-processing exoribonulease activity. Component of the mitochondrial degradosome (mtEXO) complex, that degrades 3' overhang double-stranded RNA with a 3'-to-5' directionality in an ATP-dependent manner. Required for correct processing and polyadenylation of mitochondrial mRNAs. Plays a role as a cytoplasmic RNA import factor that mediates the translocation of small RNA components, like the 5S RNA, the RNA subunit of ribonuclease P and the mitochondrial RNA-processing (MRP) RNA, into the mitochondrial matrix. Plays a role in mitochondrial morphogenesis and respiration; regulates the expression of the electron transport chain (ETC) components at the mRNA and protein levels. In the cytoplasm, shows a 3'-to-5' exoribonuclease mediating mRNA degradation activity; degrades c-myc mRNA upon treatment with IFNB1/IFN-beta, resulting in a growth arrest in melanoma cells. Regulates the stability of specific mature miRNAs in melanoma cells; specifically and selectively degrades miR-221, preferentially. Plays also a role in RNA cell surveillance by cleaning up oxidized RNAs. Binds to the RNA subunit of ribonuclease P, MRP RNA and miR-221 microRNA.[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] Publication Abstract from PubMedHuman polynucleotide phosphorylase (hPNPase) is a 3'-to-5' exoribonuclease that degrades specific mRNA and miRNA, and imports RNA into mitochondria, and thus regulates diverse physiological processes, including cellular senescence and homeostasis. However, the RNA-processing mechanism by hPNPase, particularly how RNA is bound via its various domains, remains obscure. Here, we report the crystal structure of an S1 domain-truncated hPNPase at a resolution of 2.1 A. The trimeric hPNPase has a hexameric ring-like structure formed by six RNase PH domains, capped with a trimeric KH pore. Our biochemical and mutagenesis studies suggest that the S1 domain is not critical for RNA binding, and conversely, that the conserved GXXG motif in the KH domain directly participates in RNA binding in hPNPase. Our studies thus provide structural and functional insights into hPNPase, which uses a KH pore to trap a long RNA 3' tail that is further delivered into an RNase PH channel for the degradation process. Structural RNA with short 3' tails are, on the other hand, transported but not digested by hPNPase. Crystal structure of human polynucleotide phosphorylase: insights into its domain function in RNA binding and degradation.,Lin CL, Wang YT, Yang WZ, Hsiao YY, Yuan HS Nucleic Acids Res. 2011 Dec 30. PMID:22210891[13] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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