protein consisting of membrane-spanning domains, a signal-recognition domain and
a kinase domain (Shivaji and Prakash 2010).
Recognition of signal causes auto-phosphorylation of a histidine by the kinase
and the phosphate is then transferred to an aspartate on the response regulator which
is present in the cytoplasm (Shivaji and Prakash 2010). In contrast to the
two-component signal transduction, multistep phosphorelay systems have been
investigated in both prokaryotes and eukaryotes (Appleby et al. 1996; Zhang and
Shi 2005). Suzuki et al. (2000) investigated low temperature sensor in cyanobacterial
cells. They systematically inactivated each of the 43 putative histidine kinase genes
(hik) in Synchocystis PCC 6803 and identified two histidine kinases, namely a
membrane-bound Hik33, a soluble Hik19, and a response regulator, Rer1 that
affected the inducibility of the desB gene (coding for 15 acyl lipid desaturase).
Subsequently, it was demonstrated that the response regulator 26 (Rer 26) along with
Hik33 was involved in low temperature signal transduction pathways (Suzuki et al.
2001; Mikami et al. 2002). A membrane associated two-component signal transduction pathway for cold signal perception consisting of DesK and DesR, the sensor and
the response regulator has been investigated in Bacillus subtilis (Kunst et al. 1997;
Hoch 2000; Mansilla et al. 2005). The similar CpxA-CpxR phosphorelay system,
where CpxA is a histidine kinase containing transmembrane regions and CpxR as
response regulators has also been investigated in Escherichia coli, Salmonella
typhimurium, and Yersinia pestis (De-Wult et al. 2000).
6.4.1.2 Sensing Low Temperature via Alteration in Nucleic Acid
Conformation
In bacteria, the degree of DNA super helicity varies in response to changes with the
temperature. In many studies, the expression of many genes is temperaturedependent DNA conformation, and gene regulation is mastered through changes in
DNA supercoiling (Eriksson et al. 2002). Prakash et al. (2009) have demonstrated
that inhibition of negative supercoiling leads to inhibition of cold-inducible genes
and DNA supercoiling. The topoisomerase I and II and the nucleoid-associated
protein H-NS (a small protein that binds curved regions of DNA) regulate DNA
supercoiling (Drlica 1992; Tse-Dinh et al. 1997; Dorman et al. 1999). In Shigella,
when the temperature is increased to 37
C, the ability of H-NS to bind cooperatively
to its target sequence at the VirF promoter sequences decreases due to a conformational shift in the local DNA topology, allowing transcription of VirF (Falconi et al.
1998). Similar function of StpA protein in E. coli and many other bacteria has been
studied and observed these proteins in concert with DNA appear to serve as an
additional bacterial temperature perception system (Dorman et al. 1999; Sonnefield
et al. 2001).
RNA molecules have a strong potential as temperature sensor to form pronounced
secondary and tertiary structures and ability to form intramolecular RNA:RNA
hybrids (Andersen and Delihas 1990; Lease and Belfort 2000). In E. coli and
Salmonella typhimurium expression of the dsrA gene encoding a small RpoS
regulation is dependent on the cold temperature. The temperature-depended expression of these small regulatory RNAs can modify the activity of proteins and stability
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P. K. Mishra et al.
a kinase domain (Shivaji and Prakash 2010).
Recognition of signal causes auto-phosphorylation of a histidine by the kinase
and the phosphate is then transferred to an aspartate on the response regulator which
is present in the cytoplasm (Shivaji and Prakash 2010). In contrast to the
two-component signal transduction, multistep phosphorelay systems have been
investigated in both prokaryotes and eukaryotes (Appleby et al. 1996; Zhang and
Shi 2005). Suzuki et al. (2000) investigated low temperature sensor in cyanobacterial
cells. They systematically inactivated each of the 43 putative histidine kinase genes
(hik) in Synchocystis PCC 6803 and identified two histidine kinases, namely a
membrane-bound Hik33, a soluble Hik19, and a response regulator, Rer1 that
affected the inducibility of the desB gene (coding for 15 acyl lipid desaturase).
Subsequently, it was demonstrated that the response regulator 26 (Rer 26) along with
Hik33 was involved in low temperature signal transduction pathways (Suzuki et al.
2001; Mikami et al. 2002). A membrane associated two-component signal transduction pathway for cold signal perception consisting of DesK and DesR, the sensor and
the response regulator has been investigated in Bacillus subtilis (Kunst et al. 1997;
Hoch 2000; Mansilla et al. 2005). The similar CpxA-CpxR phosphorelay system,
where CpxA is a histidine kinase containing transmembrane regions and CpxR as
response regulators has also been investigated in Escherichia coli, Salmonella
typhimurium, and Yersinia pestis (De-Wult et al. 2000).
6.4.1.2 Sensing Low Temperature via Alteration in Nucleic Acid
Conformation
In bacteria, the degree of DNA super helicity varies in response to changes with the
temperature. In many studies, the expression of many genes is temperaturedependent DNA conformation, and gene regulation is mastered through changes in
DNA supercoiling (Eriksson et al. 2002). Prakash et al. (2009) have demonstrated
that inhibition of negative supercoiling leads to inhibition of cold-inducible genes
and DNA supercoiling. The topoisomerase I and II and the nucleoid-associated
protein H-NS (a small protein that binds curved regions of DNA) regulate DNA
supercoiling (Drlica 1992; Tse-Dinh et al. 1997; Dorman et al. 1999). In Shigella,
when the temperature is increased to 37
C, the ability of H-NS to bind cooperatively
to its target sequence at the VirF promoter sequences decreases due to a conformational shift in the local DNA topology, allowing transcription of VirF (Falconi et al.
1998). Similar function of StpA protein in E. coli and many other bacteria has been
studied and observed these proteins in concert with DNA appear to serve as an
additional bacterial temperature perception system (Dorman et al. 1999; Sonnefield
et al. 2001).
RNA molecules have a strong potential as temperature sensor to form pronounced
secondary and tertiary structures and ability to form intramolecular RNA:RNA
hybrids (Andersen and Delihas 1990; Lease and Belfort 2000). In E. coli and
Salmonella typhimurium expression of the dsrA gene encoding a small RpoS
regulation is dependent on the cold temperature. The temperature-depended expression of these small regulatory RNAs can modify the activity of proteins and stability
192
P. K. Mishra et al.