J Bacteriol, February 1998, p. 647-654, Vol. 180, No. 3
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Laboratoire de Microbiologie, UA INRA, ENS.BANA, Université de Bourgogne, 21 000 Dijon, France,1 and Laboratorium voor Eiwitbiochemie en Eiwitengineering, Universiteit Gent, B-9000 Ghent, Belgium2
Received 14 July 1997/Accepted 24 November 1997
A citrate lyase (EC 4.1.3.6) was purified 25-fold from
Leuconostoc mesenteroides and was shown to contain three
subunits. The first 42 amino acids of the
subunit were identified,
as well as an internal peptide sequence spanning some 20 amino acids into the
subunit. Using degenerated primers from these sequences, we amplified a 1.2-kb DNA fragment by PCR from Leuconostoc
mesenteroides subsp. cremoris. This fragment was used
as a probe for screening a Leuconostoc genomic bank to
identify the structural genes. The 2.7-kb gene cluster encoding citrate
lyase of L. mesenteroides is organized in three open
reading frames, citD, citE, and
citF, encoding, respectively, the three citrate lyase
subunits
(acyl carrier protein [ACP]),
(citryl-S-ACP
lyase; EC 4.1.3.34), and
(citrate:acetyl-ACP transferase; EC
2.8.3.10). The gene (citC) encoding the citrate lyase
ligase (EC 6.2.1.22) was localized in the region upstream of
citD. Protein comparisons show similarities with the
citrate lyase ligase and citrate lyase of Klebsiella pneumoniae and Haemophilus influenzae. Downstream of
the citrate lyase cluster, a 1.4-kb open reading frame encoding a
52-kDa protein was found. The deduced protein is similar to CitG of the
other bacteria, and its function remains unknown. Expression of the citCDEFG gene cluster in Escherichia coli led
to the detection of a citrate lyase activity only in the presence of
acetyl coenzyme A, which is a structural analog of the prosthetic
group. This shows that the acetyl-ACP group of the citrate lyase form
in E. coli is not complete or not linked to the protein.
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