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Journal of Bacteriology, January 2000, p. 469-476, Vol. 182, No. 2
Institute for Enzyme Research, The Graduate
School, and Department of Biochemistry, College of Agriculture and
Life Sciences, University of Wisconsin
Received 19 July 1999/Accepted 2 November 1999
Lysine 2,3-aminomutase (KAM, EC 5.4.3.2.) catalyzes the
interconversion of L-lysine and L-
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Lysine 2,3-Aminomutase from Clostridium
subterminale SB4: Mass Spectral Characterization of Cyanogen
Bromide-Treated Peptides and Cloning, Sequencing, and Expression of the
Gene kamA in Escherichia coli
Madison, Madison, Wisconsin
53705
-lysine,
the first step in lysine degradation in Clostridium
subterminale SB4. KAM requires S-adenosylmethionine (SAM), which mediates hydrogen transfer in a mechanism analogous to
adenosylcobalamin-dependent reactions. KAM also contains an iron-sulfur
cluster and requires pyridoxal 5'-phosphate (PLP) for activity. In the
present work, we report the cloning and nucleotide sequencing of the
gene kamA for C. subterminale SB4 KAM and
conditions for its expression in Escherichia coli. The
cyanogen bromide peptides were isolated and characterized by mass
spectral analysis and, for selected peptides, amino acid and N-terminal
amino acid sequence analysis. PCR was performed with degenerate
oligonucleotide primers and C. subterminale SB4 chromosomal
DNA to produce a portion of kamA containing 1,029 base
pairs of the gene. The complete gene was obtained from a genomic
library of C. subterminale SB4 chromosomal DNA by use of
DNA probe analysis based on the 1,029-base pair fragment. The
full-length gene consisted of 1,251 base pairs specifying a protein of
47,030 Da, in reasonable agreement with 47,173 Da obtained by
electrospray mass spectrometry of the purified enzyme. N- and
C-terminal amino acid analysis of KAM and its cyanogen bromide peptides
firmly correlated its amino acid sequence with the nucleotide sequence
of kamA. A survey of bacterial genome databases identified
seven homologs with 31 to 72% sequence identity to KAM, none of which
were known enzymes. An E. coli expression system consisting
of pET 23a(+) plus kamA yielded unsatisfactory expression
and bacterial growth. Codon usage in kamA includes the use
of AGA for all 29 arginine residues. AGA is rarely used in E. coli, and arginine clusters at positions 4 and 5, 25 and 27, and
134, 135, and 136 apparently compound the barrier to expression. Coexpression of E. coli argU dramatically enhanced both
cell growth and expression of KAM. Purified recombinant KAM is
equivalent to that purified from C. subterminale SB4.
*
Corresponding author. Mailing address: Institute for
Enzyme Research, University of Wisconsin, 1710 University Ave.,
Madison, WI 53705. Phone: (608) 262-0055. Fax: (608) 265-2904. E-mail: frey{at}enzyme.wisc.edu.
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