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OJBTM
Online Journal of Bioinformatics ©
Volume 12(1):167-174,
2011
Detection
and classification of two-component osmoregulatory
systems
Srividhya K V and S Krishnaswamy
Centre of
Excellence in Bioinformatics, School of Biotechnology, Madurai Kamaraj University, Madurai-625021, Tamilnadu,
India
ABSTRACT
Srividhya KV, Krishnaswamy S., Detection and classification of
two-component osmoregulatory systems, Online J
Bioinformatics, 12(1):167-174, 2011. Two-component
signal transduction (TCST) systems are the principal means for coordinating
responses to environmental changes in bacteria as well as in some plants,
fungi, protozoa and archaea. These systems typically
consist of a receptor histidine kinase,
which reacts to an extracellular signal by phosphorylating
a cytoplasmic response regulator, thereby causing a
change in cellular behavior. Osmoregulation is one of
the well studied two-component system operative in bacteria and plays a crucial
role in regulating the cellular response to varied solute environments. In E
coli EnvZ, a transmembrane
protein acts as sensor and its cognate response regulator OmpR
coordinates the osmoregulatory switch by controlling
the expression of porins, OmpC
and OmpF. In this report, genome-wide identification
of osmoregulatory two-component protein orthologs has been carried out. 29 genomes are associated
with EnvZ-OmpR system, which clustered into 6
subgroups based on genus with both EnvZ and OmpR from all sources clustering together. 17 E coli encoded
two-component systems are homologous to EnvZ-OmpR.
With EnvZ and OmpR all
domain loci are conserved. The sensor and regulator partners show same
clustering trends. Hidden Markov models (HMMs) built for EnvZ
sensor kinase and OmpR
response regulators families were used to search for homologs
in other species. 39 two component systems were identified using PSI BLAST and
HMM based approach. All tend to be conserved only in the domain locus. Most of
them are systems associated with stress mediated responses. Most of sensors and
their regulators fetched from different search methods using EnvZ -OmpR systems as template
are also seen to be co-evolved. In conclusion, analysis revealed the homology
of osmoregulatory family with most of the stress
related or adaptive response related two-component systems.
Keywords: Osmoregulation, EnvZ, OmpR, Porins,
profile searches, two-component system