Characterization of Three Osmotin-Like Proteins from Plumeria rubra and Prospection for Adiponectin Peptidomimetics.

BACKGROUND: Osmotin-Like Proteins (OLPs) have been purified and characterized from different plant tissues, including latex fluids. Besides its defensive role, tobacco osmotin seems to induce adiponectin-like physiological effects, acting as an agonist. However, molecular information about this agonistic effect on adiponectin receptors has been poorly exploited and other osmotins have not been investigated yet. OBJECTIVE AND METHODS: The present study involved the characterization of three OLPs from Plumeria rubra latex and molecular docking studies to evaluate the interaction between them and adiponectin receptors (AdipoR1 and AdipoR2). RESULTS: P. rubra Osmotin-Like Proteins (PrOLPs) exhibited molecular masses from 21 to 25 kDa and isoelectric points ranging from 4.4 to 7.7. The proteins have 16 cysteine residues, which are involved in eight disulfide bonds, conserved in the same positions as other plant OLPs. The threedimensional (3D) models exhibited the three typical domains of OLPs, and molecular docking analysis showed that two PrOLP peptides interacted with two adiponectin receptors similarly to tobacco osmotin peptide. CONCLUSION: As observed for tobacco osmotin, the latex osmotins of P. rubra exhibited compatible interactions with adiponectin receptors. Therefore, these plant defense proteins (without known counterparts in humans) are potential tools to study modulation of glucose metabolism in type II diabetes, where adiponectin plays a pivotal role in homeostasis.

Thrombin and plasmin-like activities in the latices of Cryptostegia grandiflora and Plumeria rubra.

Latex proteins have drawn attention because they have shown several pharmacological activities. Herein, the fibrin(ogen)olytic activity of Cryptostegia grandiflora (CgLP) and Plumeria rubra (PrLP) latices were evaluated and characterized. Ion-exchange chromatography separated CgLP in proteolytic (CgLP PI) and nonproteolytic proteins (CgLP PII). CgLP and CgLP PI hydrolyzed azocasein in a dose-dependent manner, whereas CgLP PII and PrLP showed negligible activities. CgLP and CgLP PI accelerated plasmatic clot formation and digested all fibrinogen chains in a time/dose-dependent manner, though in a nonspecific way. CgLP and CgLP PI did not fully hydrolyze the subunits of the fibrin clot since fibrin α-chain showed resistance to proteolysis. No fibrinogenolytic activity was noticed after incubation of CgLP and CgLP PI with E-64. These results suggested that fibrinogenolytic and procoagulant activities of C. grandiflora were performed by cysteine proteases and confirm the activity of latex cysteine proteases as thrombin and plasmin-like proteins.