Catalytic core of a membrane-associated eukaryotic polyphosphate polymerase.
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.
Hothorn
Michael
M
European Molecular Biology Laboratory, Structural and Computational Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
Neumann
Heinz
H
Lenherr
Esther D
ED
Wehner
Mark
M
Rybin
Vladimir
V
Hassa
Paul O
PO
Uttenweiler
Andreas
A
Reinhardt
Monique
M
Schmidt
Andrea
A
Seiler
Jeanette
J
Ladurner
Andreas G
AG
Herrmann
Christian
C
Scheffzek
Klaus
K
Mayer
Andreas
A
D001692:Biological Transport; D002384:Catalysis; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D010770:Phosphotransferases / Q000737:chemistry* / Q000378:metabolism; D011122:Polyphosphates / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000378:metabolism
D008565:Membrane Proteins; D011122:Polyphosphates; D029701:Saccharomyces cerevisiae Proteins; D010770:Phosphotransferases