6RKD

Molybdenum storage protein under turnover conditions

Summary for 6RKD

• Entry DOI: 10.2210/pdb6rkd/pdb
• EMDB information: 4907
• Descriptor: Molybdenum storage protein subunit alpha, Molybdenum storage protein subunit beta, ADENOSINE-5'-TRIPHOSPHATE, ... (8 entities in total)
• Functional Keywords: molybdenum storage protein, atpase, metal binding protein
• Biological source: Azotobacter vinelandii (strain DJ / ATCC BAA-1303); More
• Total number of polymer chains: 12
• Total formula weight: 381493.69

Authors

Bruenle, S.,Mills, D.J.,Vonck, J.,Ermler, U. (deposition date: 2019-04-30, release date: 2019-12-18, Last modification date: 2024-05-22)

Primary citation

Brunle, S.,Eisinger, M.L.,Poppe, J.,Mills, D.J.,Langer, J.D.,Vonck, J.,Ermler, U.
Molybdate pumping into the molybdenum storage protein via an ATP-powered piercing mechanism.
Proc.Natl.Acad.Sci.USA, 2019

PubMed Abstract: The molybdenum storage protein (MoSto) deposits large amounts of molybdenum as polyoxomolybdate clusters in a heterohexameric (αβ) 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 . First, we show that molybdate, ATP, and Mg consecutively bind into the open ATP-binding groove of the β-subunit, which thereafter becomes tightly locked by fixing the previously disordered N-terminal arm of the α-subunit over the β-ATP. Next, we propose a nucleophilic attack of molybdate onto the γ-phosphate of β-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 Metβ149 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.

PubMed: 31811022
DOI: 10.1073/pnas.1913031116

Experimental method

ELECTRON MICROSCOPY (3.2 Å)