Journal of Bacteriology, July 2000, p. 3626-3631, Vol. 182, No. 13
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Theodor-Boveri-Institut für Biowissenschaften, Lehrstuhl für Mikrobiologie, Universität Würzburg, D-97074 Würzburg,1 Creatogen GmbH, D-86156 Augsburg,2 and Biotechnologie 1, Forschungszentrum Jülich GmbH, D-52425 Jülich,3 Germany
Received 25 February 1999/Accepted 3 April 2000
The functional complementation of two Escherichia coli strains defective in the succinylase pathway of meso-diaminopimelate (meso-DAP) biosynthesis with a Bordetella pertussis gene library resulted in the isolation of a putative dap operon containing three open reading frames (ORFs). In line with the successful complementation of the E. coli dapD and dapE mutants, the deduced amino acid sequences of two ORFs revealed significant sequence similarities with the DapD and DapE proteins of E. coli and many other bacteria which exhibit tetrahydrodipicolinate succinylase and N-succinyl-L,L-DAP desuccinylase activity, respectively. The first ORF within the operon showed significant sequence similarities with transaminases and contains the characteristic pyridoxal-5'-phosphate binding motif. Enzymatic studies revealed that this ORF encodes a protein with N-succinyl-L,L-DAP aminotransferase activity converting N-succinyl-2-amino-6-ketopimelate, the product of the succinylase DapD, to N-succinyl-L,L-DAP, the substrate of the desuccinylase DapE. Therefore, this gene appears to encode the DapC protein of B. pertussis. Apart from the pyridoxal-5'-phosphate binding motif, the DapC protein does not show further amino acid sequence similarities with the only other known enzyme with N-succinyl-L,L-DAP aminotransferase activity, ArgD of E. coli.
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