4gem
From Proteopedia
Crystal structure of Zucchini (K171A)
Structural highlights
FunctionZUC_DROME Cardiolipin hydrolase present at the mitochondrial outer membrane required for piRNA metabolic process. Acts by catalyzing the hydrolysis of cardiolipin (diphosphatidylglycerol) to form phosphatidate (phosphatidic acid or PA) at the mitochondrial outer membrane surface, promoting the piRNA metabolic process. Plays a key role in primary biogenesis of piRNAs and is required during oogenesis to repress transposable elements and prevent their mobilization. piRNAs mediate the repression of transposable elements during meiosis by forming complexes composed of piRNAs and Piwi proteins and govern the methylation and subsequent repression of transposons. Involved in trans-silencing effect (TSE), a homology-dependent repression mechanism by which a P-transgene inserted in subtelomeric heterochromatin via its role in piRNA biogenesis.[1] [2] [3] [4] [5] [6] [7] Publication Abstract from PubMedPIWI-interacting RNAs (piRNAs) silence transposons to maintain genome integrity in animal germ lines. piRNAs are classified as primary and secondary piRNAs, depending on their biogenesis machinery. Primary piRNAs are processed from long non-coding RNA precursors transcribed from piRNA clusters in the genome through the primary processing pathway. Although the existence of a ribonuclease participating in this pathway has been predicted, its molecular identity remained unknown. Here we show that Zucchini (Zuc), a mitochondrial phospholipase D (PLD) superfamily member, is an endoribonuclease essential for primary piRNA biogenesis. We solved the crystal structure of Drosophila melanogaster Zuc (DmZuc) at 1.75 A resolution. The structure revealed that DmZuc has a positively charged, narrow catalytic groove at the dimer interface, which could accommodate a single-stranded, but not a double-stranded, RNA. DmZuc and the mouse homologue MmZuc (also known as Pld6 and MitoPLD) showed endoribonuclease activity for single-stranded RNAs in vitro. The RNA cleavage products bear a 5'-monophosphate group, a hallmark of mature piRNAs. Mutational analyses revealed that the conserved active-site residues of DmZuc are critical for the ribonuclease activity in vitro, and for piRNA maturation and transposon silencing in vivo. We propose a model for piRNA biogenesis in animal germ lines, in which the Zuc endoribonuclease has a key role in primary piRNA maturation. Structure and function of Zucchini endoribonuclease in piRNA biogenesis.,Nishimasu H, Ishizu H, Saito K, Fukuhara S, Kamatani MK, Bonnefond L, Matsumoto N, Nishizawa T, Nakanaga K, Aoki J, Ishitani R, Siomi H, Siomi MC, Nureki O Nature. 2012 Nov 8;491(7423):284-7. doi: 10.1038/nature11509. Epub 2012 Oct 14. PMID:23064230[8] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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