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  • Title: Subtle alteration of the active site of ribulose bisphosphate carboxylase/oxygenase by concerted site-directed mutagenesis and chemical modification.
    Author: Smith HB, Larimer FW, Hartman FC.
    Journal: Biochem Biophys Res Commun; 1988 Apr 29; 152(2):579-84. PubMed ID: 2896501.
    Abstract:
    Both activities of ribulose bisphosphate carboxylase/oxygenase are dependent on carbamylation by CO2 of a specific lysyl epsilon-amino group (Lys-191 of the enzyme from Rhodospirillum rubrum). To examine the stringency of the requirement for this lysyl side chain, Lys-191 was converted to an aminoethylcysteinyl residue (net replacement of a gamma-methylene group by a sulfur atom) by a combination of site-directed mutagenesis and subsequent chemical modification. The purified Cys-191 mutant was totally devoid of both carboxylase and oxygenase activities. However, this mutant protein exhibited tight-binding of the transition-state analogue, 2-carboxyarabinitol bisphosphate, a property heretofore ascribed solely to the carbamylated form of the carboxylase. Treatment of the mutant protein with ethylene imine restored catalytic activity to 4-7% of the wild-type level. The carboxylase:oxygenase activity ratio of the aminoethylated protein was unperturbed relative to that of wild-type enzyme.
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