The lysine-rich motif of intrinsically disordered stress protein CDeT11-24 from Craterostigma plantagineum is responsible for phosphatidic acid binding and protection of enzymes from damaging effects caused by desiccation

Abstract

The late embryogenesis abundant (LEA)-like protein CDeT11-24 is one of the major desiccation-related phosphoproteins of the resurrection plant Craterostigma plantagineum. In this study, it was shown that CDeT11-24 is mostly intrinsically disordered and protects two different enzymes, citrate synthase and lactate dehydrogenase, against damaging effects caused by desiccation. Lipid-binding assays revealed that CDeT11-24 is able to interact with phosphatidic acid, although electrostatic repulsion was expected due to the overall negative net charge of the protein under the tested physiological conditions. CDeT11-24 carries an N-terminal lysine-rich sequence, which is predicted to form an amphipathic α-helix. Analysis of the truncated CDeT11-24 protein identified this region to be responsible for both activities: enzyme protection and phosphatidic acid interaction. Possible functions of the CDeT11-24 protein are discussed in the context of desiccation tolerance.

Abbreviations:

ABA	abscisic acid;
CD	circular dichroism;
CS	citrate synthase;
IDP	intrinsically disordered protein;
LDH	lactate dehydrogenase;
LEA	late embryogenesis abundant;
PA	phosphatidic acid;
PC	phosphatidylcholine;
TFE	trifluoroethanol.