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Artificial RNA Polymerase II Elongation Complexes for Dissecting Co-transcriptional RNA Processing Events
Published on: May 13, 2019
Catalytic core of a membrane-associated eukaryotic polyphosphate polymerase
Michael Hothorn1, Heinz Neumann, Esther D Lenherr
1European Molecular Biology Laboratory, Structural and Computational Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
Abstract:
Polyphosphate (polyP) occurs ubiquitously in cells, but its functions are poorly understood and its synthesis has only been characterized in bacteria. Using x-ray crystallography, we identified a eukaryotic polyphosphate polymerase within the membrane-integral vacuolar transporter chaperone (VTC) complex. A 2.6 angstrom crystal structure of the catalytic domain grown in the presence of adenosine triphosphate (ATP) reveals polyP winding through a tunnel-shaped pocket. Nucleotide- and phosphate-bound structures suggest that the enzyme functions by metal-assisted cleavage of the ATP gamma-phosphate, which is then in-line transferred to an acceptor phosphate to form polyP chains. Mutational analysis of the transmembrane domain indicates that VTC may integrate cytoplasmic polymer synthesis with polyP membrane translocation. Identification of the polyP-synthesizing enzyme opens the way to determine the functions of polyP in lower eukaryotes.
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