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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, Onl J Bioinform., 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
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