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Related Experiment Video

Updated: Jul 20, 2026

Structure-Guided Design and Development of Novel Cyclophilin A Inhibitors and Ganoderiol-F Derivatives: An In-Silico Approach

Structure-Guided Design and Development of Novel Cyclophilin A Inhibitors and Ganoderiol-F Derivatives: An In-Silico Approach

Published on: June 23, 2026

Eukaryotic cyclophilin as a molecular switch for effector activation.

Gitta Coaker¹, George Zhu, Zhaofeng Ding

¹Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, CA 94720, USA.

Molecular Microbiology

|September 14, 2006

Summary

Plant pathogenic bacteria deliver unfolded effector proteins, like AvrRpt2, into host cells. Arabidopsis cyclophilin ROC1 binds and folds AvrRpt2 via peptidyl-prolyl cis/trans isomerization, activating its protease activity.

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Published on: June 15, 2017

Area of Science:

Plant pathology
Molecular biology
Protein biochemistry

Background:

Gram-negative bacteria deliver effector proteins into host cells via secretion systems.
Effector proteins are often delivered in an unfolded, inactive state.
AvrRpt2 is a Pseudomonas syringae effector protein and a cysteine protease activated by Arabidopsis cyclophilin.

Purpose of the Study:

To elucidate the mechanism by which Arabidopsis cyclophilin ROC1 activates the Pseudomonas syringae effector AvrRpt2.
To investigate the role of ROC1's peptidyl-prolyl cis/trans isomerase (PPIase) activity in AvrRpt2 activation.
To identify the binding sites and structural changes involved in AvrRpt2 activation.

Main Methods:

Site-directed mutagenesis to create ROC1 mutants lacking PPIase activity.
Nuclear magnetic resonance (NMR) spectroscopy to observe structural changes in AvrRpt2.
In vitro binding assays to identify ROC1 consensus binding sequences in AvrRpt2.

Main Results:

ROC1 mutants lacking PPIase activity failed to activate AvrRpt2.
NMR spectroscopy demonstrated a transition of AvrRpt2 from an unfolded to a folded state upon ROC1 interaction.
ROC1 binds AvrRpt2 at four GPxL motifs, located near the catalytic triad, which are essential for protease activity in vitro and in planta.

Conclusions:

Arabidopsis cyclophilin ROC1 activates the Pseudomonas syringae effector AvrRpt2 through its PPIase activity.
ROC1 induces proper folding of AvrRpt2 by binding to specific GPxL motifs, thereby enabling its function as a protease within the plant cell.
This mechanism highlights the importance of protein folding and isomerization in effector protein activation during plant pathogenesis.