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Journal of Bacteriology, April 2000, p. 1828-1833, Vol. 182, No. 7
Department of Microbiology and
Immunology1 and Neurology Microscopy
Core Facility,3 Emory University School of
Medicine, Atlanta, 30322, and Instituto de Tecnologia
Química e Biológica, New University of Lisbon, 2781-901 Oeiras Codex, Portugal2
Received 28 October 1999/Accepted 17 January 2000
During endospore formation in Bacillus subtilis, over
two dozen polypeptides are assembled into a multilayered structure
known as the spore coat, which protects the cortex peptidoglycan (PG) and permits efficient germination. In the initial stages of coat assembly a protein known as CotE forms a ring around the forespore. A
second morphogenetic protein, SpoVID, is required for maintenance of
the CotE ring during the later stages, when most of proteins are
assembled into the coat. Here, we report on a protein that appears to
associate with SpoVID during the early stage of coat assembly. This
protein, which we call SafA for SpoVID-associated factor A, is encoded
by a locus previously known as yrbA. We confirmed the
results of a previous study that showed safA mutant spores have defective coats which are missing several proteins. We have extended these studies with the finding that SafA and SpoVID were coimmunoprecipitated by anti-SafA or anti-SpoVID antiserum from whole-cell extracts 3 and 4 h after the onset of sporulation. Therefore, SafA may associate with SpoVID during the early stage of
coat assembly. We used immunogold electron microscopy to localize SafA
and found it in the cortex, near the interface with the coat in mature
spores. SafA appears to have a modular design. The C-terminal region of
SafA is similar to those of several inner spore coat proteins. The
N-terminal region contains a sequence that is conserved among proteins
that associate with the cell wall. This motif in the N-terminal region
may target SafA to the PG-containing regions of the developing spore.
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Morphogenetic Proteins SpoVID and SafA Form a
Complex during Assembly of the Bacillus subtilis Spore
Coat
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, Emory University School of Medicine,
Atlanta, GA 30332. Phone: (404) 727-5969. Fax: (404) 727-3659. E-mail: moran{at}microbio.emory.edu.
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