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1 February 1995

Purification and initial characterization of the ATP:corrinoid adenosyltransferase encoded by the cobA gene of Salmonella typhimurium


The cobA gene of Salmonella typhimurium and its product were overexpressed to approximately 20% of the total cell protein. CobA was purified to 98% homogeneity; N-terminal sequence analysis (21 residues) of homogeneous protein confirmed the predicted amino acid sequence. ATP:corrinoid adenosyltransferase activity was demonstrated in vitro to be associated with CobA. This activity was optimal at pH 8 and 37 degrees C. A quantitative preference was determined for Mn(II) cations and ATP. The apparent Km of CobA for ATP was 2.8 microM, and that for cob(I)alamin was 5.2 microM. Vmax was measured at 0.43 nmol/min. Cobinamide served as the substrate for CobA to yield adenosylcobinamide. Activity was stable at 4 degrees C for several weeks but was lost rapidly at room temperature (50% overnight). Dithiothreitol was required to maintain the enzymatic activity of CobA.

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Published In

cover image Journal of Bacteriology
Journal of Bacteriology
Volume 177Number 4February 1995
Pages: 921 - 925
PubMed: 7860601


Published online: 1 February 1995


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S Suh
Department of Bacteriology, University of Wisconsin-Madison 53706-1567.
J C Escalante-Semerena
Department of Bacteriology, University of Wisconsin-Madison 53706-1567.

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