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Journal of Bacteriology, September 1998, p. 4950-4954, Vol. 180, No. 18
Institute of Biotechnology, Technical
University Berlin, Berlin, Germany,1 and
Bijvoet Center for Biomolecular Research, Department of Mass
Spectrometry, Utrecht University, 3584 CA Utrecht, The
Netherlands2
Received 12 February 1998/Accepted 17 July 1998
Rhizobial capsular polysaccharides (RKPs) play an important role in
the development of a nitrogen-fixing symbiosis with the plant host and
in Sinorhizobium meliloti AK631 functional
rkpABCDEF genes are required for the production of RKPs.
After cloning the rkpF gene, we overexpressed and purified
the derived protein product (RkpF) in Escherichia coli.
Like acyl carrier protein (ACP), the RkpF protein can be labeled in
vivo with radioactive
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Characterization of a Novel Acyl Carrier Protein, RkpF, Encoded
by an Operon Involved in Capsular Polysaccharide Biosynthesis
in Sinorhizobium meliloti
-alanine added to the growth medium. If
homogeneous RkpF protein is incubated with radiolabeled coenzyme A in
the presence of purified holo-ACP synthase from E. coli, an
in vitro transfer of 4'-phosphopantetheine to the RkpF protein can be
observed. The conversion from apo-RkpF protein to holo-RkpF protein
seems to go along with a major conformational change of the protein
structure, because the holo-RkpF protein runs significantly faster
on native polyacrylamide gel electrophoresis than the apo-RkpF protein.
Electrospray mass spectrometric analysis reveals a mass of 9,585 for
the apo-RkpF protein and a mass of 9,927 for the holo-RkpF protein. Our
data show that RkpF is a novel ACP.
*
Corresponding author. Mailing address: Technische
Universität Berlin, Institut für Biotechnologie, FG
Technische Biochemie, Seestraße 13, D-13353 Berlin, Germany.
Phone: 49-30-314-27509. Fax: 49-30-4536-067. E-mail:
geig1332{at}mailszrz.zrz.tu-berlin.de.
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