Requirement of carbon dioxide for in vitro assembly of the urease nickel metallocenter.
Assembly of protein metallocenters is not well understood. Urease offers a tractable system for examination of this process. Formation of the urease metallocenter in vivo is known to require four accessory proteins: UreD, postulated to be a urease-specific molecular chaperone; UreE, a nickel(II)-binding protein; and UreF and UreG, of unknown function. Activation of purified Klebsiella aerogenes urease apoprotein was accomplished in vitro by providing carbon dioxide (half-maximal activation at approximately 0.2 percent carbon dioxide) in addition to nickel ion. Activation coincided with carbon dioxide incorporation into urease in a pH-dependent reaction (pKa > or = 9, where Ka is the acid constant). The concentration of carbon dioxide also affected the amount of activation of UreD-urease apoprotein complexes. These results suggest that carbon dioxide binding to urease apoprotein generates a ligand that facilitates productive nickel binding.
Department of Microbiology, Michigan State University, East Lansing 48824.
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Park
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Hausinger
D001059:Apoproteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism*; D004789:Enzyme Activation; D006863:Hydrogen-Ion Concentration; D007711:Klebsiella pneumoniae / Q000201:enzymology; D009532:Nickel / Q000378:metabolism*; D014510:Urease / Q000378:metabolism*
D001059:Apoproteins; D001426:Bacterial Proteins; C086767:UreD protein, Bacteria; D002245:Carbon Dioxide; D009532:Nickel; D014510:Urease