6ris
The Kb42S variant of the molybdenum storage protein
Structural highlights
FunctionMOSB_AZOVD Intracellular storage of molybdenum. Binds polyoxomolybdates. Can bind at least 90 molybdenum atoms per protein molecule. Publication Abstract from PubMedThe molybdenum storage protein (MoSto) deposits large amounts of molybdenum as polyoxomolybdate clusters in a heterohexameric (alphabeta)3 cage-like protein complex under ATP consumption. Here, we suggest a unique mechanism for the ATP-powered molybdate pumping process based on X-ray crystallography, cryoelectron microscopy, hydrogen-deuterium exchange mass spectrometry, and mutational studies of MoSto from Azotobacter vinelandii First, we show that molybdate, ATP, and Mg(2+) consecutively bind into the open ATP-binding groove of the beta-subunit, which thereafter becomes tightly locked by fixing the previously disordered N-terminal arm of the alpha-subunit over the beta-ATP. Next, we propose a nucleophilic attack of molybdate onto the gamma-phosphate of beta-ATP, analogous to the similar reaction of the structurally related UMP kinase. The formed instable phosphoric-molybdic anhydride becomes immediately hydrolyzed and, according to the current data, the released and accelerated molybdate is pressed through the cage wall, presumably by turning aside the Metbeta149 side chain. A structural comparison between MoSto and UMP kinase provides valuable insight into how an enzyme is converted into a molecular machine during evolution. The postulated direct conversion of chemical energy into kinetic energy via an activating molybdate kinase and an exothermic pyrophosphatase reaction to overcome a proteinous barrier represents a novelty in ATP-fueled biochemistry, because normally, ATP hydrolysis initiates large-scale conformational changes to drive a distant process. Molybdate pumping into the molybdenum storage protein via an ATP-powered piercing mechanism.,Brunle S, Eisinger ML, Poppe J, Mills DJ, Langer JD, Vonck J, Ermler U Proc Natl Acad Sci U S A. 2019 Dec 6. pii: 1913031116. doi:, 10.1073/pnas.1913031116. PMID:31811022[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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