- Email: [email protected]
Analysis of regulatory mechanism of sulfate permease expression in cyanobacteria
24
Journal of
Abstracts
B07
AN ALYS IS
OF
REGU LATORY
PERMEASE
EXPRESSION
IN
MECHANIS M
Inorganic Biochemistry OF
S U LFATE
CYANOBACTERIA
E. S u z u ~ , M. Aoki and K. Uchiyama
Department of Biology, Ibaraki University, 2-1-1 Bunkyo, Mito 310, Japan Sulfate is utilized as the source of organic sulfur compounds in cyanobacteria. sulfate assimilation is the uptake of this ion across the cytoplasmic membrane.
The initial step of
Active transport of sulfate
is observed under sulfur deficient conditions as the result of the induction of sulfate permease.
Sulfate
permease in cyanobacteria is a member of ABC transporter superfamily composed of a periplasmic substrate binding protein, trans-membrane subunits, and a cytoplasmic ATP-hydrolyzing subunit, encoded by sbpA, cysT and cysW, and cysA genes, respectively [1].
On the chromosome of a
unicellular cyanobacterium, Synechococcus sp. strain PCC 7942, sbpA and cysA genes are adjacent to Genes cysT and cysW are located downstream of, and probably co-
each other and divergently oriented. transcribed with sbpA.
These genes therefore constitute two transcriptional units.
Expression of sbpA
and cysA genes during sulfur starvation was studied. The transcriptional initiation sites of sbpA and cysA genes, as determined by primer extension analysis, were at 106 and 68 nucleotides upstream of the coding region, respectively.
The distance
between the two sites are 25 nucleotides and therefore the two promoters in the opposite directions may overlap each other.
The transcripts were observed only in the sulfur deficient conditions.
The intergenic DNA fragment flanked by 5' portions of sbpA and cysA was used to construct translational fusions with a reporter gene, gusA encoding [3-glucuronidase [2]. then determined in the cyanobacterial transformants harboring the fusions.
The GUS activity was The GUS activity in the
transformants with the sbpA-gusA fusion was much higher in sulfur deficient than in sulfur sufficient conditions.
In contrast, the activity in the transformants with the cysA-gusA fusion was high
irrespective of sulfur availability.
The result suggests that the intergenic region is involved in the
regulation of sbpA expression, while an additional regulatory DNA sequence is necessary for repression of cysA in sulfur sufficient conditions. 1.
D.E. Laudenbach and A.R. Grossman, J. Bacteriol., 173, 2739 (1991).
2.
K.J. Wilson, S.G. Hughes and R.A. Jefferson, in GUS Protocols: Using the GUS Gene as a
Reporter of Gene Expression, S.R. Gallagher, Ed., Academic Press, San Diego, 1992, p.7.
Journal of
Abstracts
B07
AN ALYS IS
OF
REGU LATORY
PERMEASE
EXPRESSION
IN
MECHANIS M
Inorganic Biochemistry OF
S U LFATE
CYANOBACTERIA
E. S u z u ~ , M. Aoki and K. Uchiyama
Department of Biology, Ibaraki University, 2-1-1 Bunkyo, Mito 310, Japan Sulfate is utilized as the source of organic sulfur compounds in cyanobacteria. sulfate assimilation is the uptake of this ion across the cytoplasmic membrane.
The initial step of
Active transport of sulfate
is observed under sulfur deficient conditions as the result of the induction of sulfate permease.
Sulfate
permease in cyanobacteria is a member of ABC transporter superfamily composed of a periplasmic substrate binding protein, trans-membrane subunits, and a cytoplasmic ATP-hydrolyzing subunit, encoded by sbpA, cysT and cysW, and cysA genes, respectively [1].
On the chromosome of a
unicellular cyanobacterium, Synechococcus sp. strain PCC 7942, sbpA and cysA genes are adjacent to Genes cysT and cysW are located downstream of, and probably co-
each other and divergently oriented. transcribed with sbpA.
These genes therefore constitute two transcriptional units.
Expression of sbpA
and cysA genes during sulfur starvation was studied. The transcriptional initiation sites of sbpA and cysA genes, as determined by primer extension analysis, were at 106 and 68 nucleotides upstream of the coding region, respectively.
The distance
between the two sites are 25 nucleotides and therefore the two promoters in the opposite directions may overlap each other.
The transcripts were observed only in the sulfur deficient conditions.
The intergenic DNA fragment flanked by 5' portions of sbpA and cysA was used to construct translational fusions with a reporter gene, gusA encoding [3-glucuronidase [2]. then determined in the cyanobacterial transformants harboring the fusions.
The GUS activity was The GUS activity in the
transformants with the sbpA-gusA fusion was much higher in sulfur deficient than in sulfur sufficient conditions.
In contrast, the activity in the transformants with the cysA-gusA fusion was high
irrespective of sulfur availability.
The result suggests that the intergenic region is involved in the
regulation of sbpA expression, while an additional regulatory DNA sequence is necessary for repression of cysA in sulfur sufficient conditions. 1.
D.E. Laudenbach and A.R. Grossman, J. Bacteriol., 173, 2739 (1991).
2.
K.J. Wilson, S.G. Hughes and R.A. Jefferson, in GUS Protocols: Using the GUS Gene as a
Reporter of Gene Expression, S.R. Gallagher, Ed., Academic Press, San Diego, 1992, p.7.