Journal of Bacteriology, September 2000, p. 4677-4687, Vol. 182, No. 17
Lehrstuhl für Technische Mikrobiologie,
Universität Dortmund,1 and
Max-Planck-Institut für Molekulare
Physiologie,3 D-44227 Dortmund, and
Max-Delbrück-Centrum für Molekulare Medizin,
D-13122 Berlin,2 Germany
Received 28 January 2000/Accepted 25 May 2000
The gene region coding for lithotrophic sulfur oxidation of
Paracoccus pantotrophus GB17 is located on a 13-kb insert
of plasmid pEG12. Upstream of the previously described six open reading
frames (ORFs) soxABCDEF with a partial sequence of
soxA and soxF (C. Wodara, F. Bardischewsky, and
C. G. Friedrich, J. Bacteriol. 179:5014-5023, 1997), 4,350 bp
were sequenced. The sequence completed soxA, and uncovered
six new ORFs upstream of soxA, designated ORF1, ORF2, and
ORF3, and soxXYZ. ORF1 could encode a 275-amino-acid
polypeptide of 29,332 Da with a 61 to 63% similarity to LysR
transcriptional regulators. ORF2 could encode a 245-amino-acid
polypeptide of 26,022 Da with the potential to form six transmembrane
helices and with a 48 to 51% similarity to proteins involved in redox transport in cytochrome c biogenesis. ORF3 could encode a
periplasmic polypeptide of 186 amino acids of 20,638 Da with a
similarity to thioredoxin-like proteins and with a putative signal
peptide of 21 amino acids. Purified SoxXA, SoxYZ, and SoxB are
essential for thiosulfate or sulfite-dependent cytochrome c
reduction in vitro. N-terminal and internal amino acid sequences
identified SoxX, SoxY, SoxZ, and SoxA to be coded by the respective
genes. The molecular masses of the mature proteins determined by
electrospray ionization spectroscopy (SoxX, 14,834 Da; SoxY, 11,094 Da;
SoxZ, 11,717 Da; and SoxA, 30,452 Da) were identical or close to those deduced from the nucleotide sequence with differences for the covalent
heme moieties. SoxXA represents a novel type of periplasmic c-type cytochromes, with SoxX as a monoheme and SoxA as a
hybrid diheme cytochrome c. SoxYZ is an
as-yet-unprecedented soluble protein. SoxY has a putative signal
peptide with a twin arginine motif and possibly cotransports SoxZ to
the periplasm. SoxYZ neither contains a metal nor a complex redox
center, as proposed for proteins likely to be transported via the Tat system.
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Novel Genes Coding for Lithotrophic Sulfur
Oxidation of Paracoccus pantotrophus GB17
*
Corresponding author. Mailing address: Lehrstuhl
für Technische Mikrobiologie, Universität Dortmund,
Emil-Figge-Strasse 66, D-44227 Dortmund, Germany. Phone: (49)
231-755-5115. Fax: (49) 231-755- 5118. E-mail:
friedric{at}ct.uni-dortmund.de.
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