J Bacteriol, May 1998, p. 2616-2622, Vol. 180, No. 10
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
and
Unité d'Immunotechnologie et
Microbiologie Moléculaires,
Received 26 December 1997/Accepted 11 March 1998
Reversible protein phosphorylation plays important roles in signal
transduction. One gene, prpA, encoding a protein similar to
eukaryotic types of phosphoprotein phosphatases PP1, PP2A, and PP2B,
was cloned from the nitrogen-fixing cyanobacterium Anabaena sp. strain PCC 7120. Interestingly, a eukaryotic-type protein kinase
gene, pknE, was found 301 bp downstream of
prpA. This unusual genetic arrangement provides the
opportunity for study about how the balance between protein
phosphorylation and dephosphorylation can regulate cellular activities.
Both proteins were overproduced in Escherichia coli and
used to raise polyclonal antibodies. Immunodetection and RNA/DNA
hybridization experiments suggest that these two genes are unlikely to
be coexpressed, despite their close genetic linkage. PrpA is expressed
constitutively under different nitrogen conditions, while PknE
expression varies according to the nature of the nitrogen source.
Inactivation analysis in vivo suggests that PrpA and PknE function to
ensure a correct level of phosphorylation of the targets in order to
regulate similar biological processes such as heterocyst structure
formation and nitrogen fixation.
*
Corresponding author. Mailing address: Unité
d'Immunotechnologie et Microbiologie Moléculaires, ESBS,
Boulevard Sébastien Brandt, F-67400 Illkirch, France. Phone: (33)
3 8865 5290. Fax: (33) 3 8865 5330. E-mail:
cczhang{at}esbs1.u-strasbg.fr.
Present address: LAB, 92270 Bois-Colombes, France.
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