A. Poplawski et al., The ftsZ gene of Haloferax mediterranei: sequence, conserved gene order, and visualization of the FtsZ ring, GENE, 242(1-2), 2000, pp. 357-367
We sequenced the ftsZ gene region of the halophilic archaeon Haloferax medi
terranei and mapped the transcription start sites for the ftsZ gene. The ge
ne encoded a 363-amino-acid long FtsZ protein with a predicted molecular ma
ss of 38 kDa and an isoelectric point of 4.2. A high level of similarity to
the FtsZ protein of Haloferax volcanii was apparent, with 97 and 90% ident
ity at the amino acid and nucleotide levels, respectively. Structural conse
rvation at the protein level was shown by visualization of the FtsZ ring st
ructure in H. mediterranei cells using an antiserum raised against FtsZ of
H. volcanii FtsZ rings were observed in cells in different stages of divisi
on, including cells with pleomorphic shapes and cells that appeared to be u
ndergoing asymmetric division. Cells were also observed that displayed cons
triction-like invaginations in the absence of an FtsZ ring, indicating that
morphological data are not sufficient to determine whether pleomorphic Hal
oferax cells are undergoing cell division. Both the upstream and downstream
gene order in the ftsZ region was found to be conserved within the genus H
aloferax. Furthermore, the downstream gene order, which includes the secE a
nd nusG genes, is conserved in almost all euryarchaea sequenced to date. Th
e secE and nusG genes are likely to be transcriptionally and translationall
y coupled in Haloferax, and this co-expression may have been a selective fo
rce that has contributed to keeping the gene cluster intact. (C) 2000 Elsev
ier Science B.V. All rights reserved.