Proteomic studies have established that Trz1, Nuc1 and mutarotase form a complex in yeast. Trz1 is a β-lactamase-type RNase composed of two β-lactamase-type domains connected by a long linker that is responsible for the endonucleolytic cleavage at the 3′-end of tRNAs during the maturation process (RNase Z activity); Nuc1 is a dimeric mitochondrial nuclease involved in apoptosis, while mutarotase (encoded by YMR099C) catalyzes the conversion between the α- and β-configuration of glucose-6-phosphate. Using gel filtration, small angle X-ray scattering and electron microscopy, we demonstrated that Trz1, Nuc1 and mutarotase form a very stable heterohexamer, composed of two copies of each of the three subunits. A Nuc1 homodimer is at the center of the complex, creating a two-fold symmetry and interacting with both Trz1 and mutarotase. Enzymatic characterization of the ternary complex revealed that the activities of Trz1 and mutarotase are not affected by complex formation, but that the Nuc1 activity is completely inhibited by mutarotase and partially by Trz1. This suggests that mutarotase and Trz1 might be regulators of the Nuc1 apoptotic nuclease activity.
An epifluorescence image of HEK293 cells expressing mKate2–GPER (red) and loaded with the Ca2+ indicator fura-2/AM (blue). The approach allows for direct comparison of Ca2+ signals in cells transfected with or without mKate2–GPER in the same microscopic field. In this issue of the Biochemical Journal, Terry et al. report on how activation of GPER (G protein-coupled estrogen receptor 1) “clamps” cytoplasmic Ca2+ signals via suppression of store-operated Ca2+ entry and Ca2+ efflux; see pages 3627–3642 for details.
Trz1, the long form RNase Z from yeast, forms a stable heterohexamer with endonuclease Nuc1 and mutarotase
Miao Ma, Ines Li de la Sierra-Gallay, Noureddine Lazar, Olivier Pellegrini, Jean Lepault, Ciarán Condon, Dominique Durand, Herman van Tilbeurgh; Trz1, the long form RNase Z from yeast, forms a stable heterohexamer with endonuclease Nuc1 and mutarotase. Biochem J 1 November 2017; 474 (21): 3599–3613. doi: https://doi.org/10.1042/BCJ20170435
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