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Functional analysis of the two cyclophilin isoforms of Sinorhizobium meliloti

Eirini-Evangelia Thomloudi1, Aggeliki Skagia1, Anastasia Venieraki1

  • 1Laboratory of General and Agricultural Microbiology, Faculty of Crop Science, Agricultural University of Athens, Iera Odos 75, 11855, Athens, Greece.

World Journal of Microbiology & Biotechnology
|January 7, 2017
PubMed

Insights

Sinorhizobium meliloti cyclophilins, encoded by ppiA and ppiB, isomerize peptides but lack chaperone activity. Their expression enhances E. coli viability under heat and salt stress, supporting roles in stress response.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Biochemistry

Background:

  • Sinorhizobium meliloti is a nitrogen-fixing bacterium.
  • It possesses two genes, ppiA and ppiB, encoding cyclophilin isoforms.
  • Cyclophilins belong to the peptidyl prolyl cis/trans isomerase (PPIase) superfamily.

Purpose of the Study:

  • To functionally characterize the two S. meliloti cyclophilins.
  • To investigate their enzymatic activity and potential chaperone function.
  • To assess their role in bacterial stress tolerance.

Main Methods:

  • Recombinant expression and purification of S. meliloti cyclophilins.
  • Enzymatic assay using Suc-AAPF-pNA substrate to measure PPIase activity.
  • Citrate synthase thermal aggregation assay to evaluate chaperone activity.
  • Assessing E. coli BL21 viability under abiotic stress (heat, salt) with cyclophilin expression.

Main Results:

  • Both recombinant cyclophilins demonstrated peptidyl prolyl cis/trans isomerase (PPIase) activity.
  • Neither cyclophilin exhibited chaperone activity in the citrate synthase assay.
  • Expression of both cyclophilins significantly increased E. coli BL21 viability under heat and salt stress.

Conclusions:

  • S. meliloti cyclophilins possess PPIase activity but not chaperone function.
  • These cyclophilins contribute to bacterial tolerance against abiotic stress conditions.
  • Findings support previous high-throughput studies on the role of S. meliloti cyclophilins in stress response.
Keywords:
Abiotic stressCyclophilinPeptidyl-prolyl cis/trans isomeraseSinorhizobium meliloti

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