Synthetic peptides derived from the C-terminal 6kDa region of Plasmodium falciparum SERA5 inhibit the enzyme activity and malaria parasite development.
BACKGROUND
Plasmodium falciparum serine repeat antigen 5 (PfSERA5) is an abundant blood stage protein that plays an essential role in merozoite egress and invasion. The native protein undergoes extensive proteolytic cleavage that appears to be tightly regulated. PfSERA5 N-terminal fragment is being developed as vaccine candidate antigen. Although PfSERA5 belongs to papain-like cysteine protease family, its catalytic domain has a serine in place of cysteine at the active site.


METHODS
In the present study, we synthesized a number of peptides from the N- and C-terminal regions of PfSERA5 active domain and evaluated their inhibitory potential.


RESULTS
The final proteolytic step of PfSERA5 involves removal of a C-terminal ~6kDa fragment that results in the generation of a catalytically active ~50kDa enzyme. In the present study, we demonstrate that two of the peptides derived from the C-terminal ~6kDa region inhibit the parasite growth and also cause a delay in the parasite development. These peptides reduced the enzyme activity of the recombinant protein and co-localized with the PfSERA5 protein within the parasite, thereby indicating the specific inhibition of PfSERA5 activity. Molecular docking studies revealed that the inhibitory peptides interact with the active site of the protein. Interestingly, the peptides did not have an effect on the processing of PfSERA5.


CONCLUSIONS
Our observations indicate the temporal regulation of the final proteolytic cleavage step that occurs just prior to egress.


CONCLUSIONS
These results reinforce the role of PfSERA5 for the intra-erythrocytic development of malaria parasite and show the role of carboxy terminal ~6kDa fragments in the regulation of PfSERA5 activity. The results also suggest that final cleavage step of PfSERA5 can be targeted for the development of new anti-malarials.
International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India.
Shivani
S
Kanodia
International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India.
Gautam
G
Kumar
Dipartimento di Scienze Farmaceutiche, Facoltà di Scienze del Farmaco, Università degli Studi di Milano, Via L. Mangiagalli 25, 20133 Milan, Italy.
Luca
L
Rizzi
Dipartimento di Scienze Farmaceutiche, Facoltà di Scienze del Farmaco, Università degli Studi di Milano, Via L. Mangiagalli 25, 20133 Milan, Italy.
Alessandro
A
Pedretti
The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3050, Australia.
Anthony N
AN
Hodder
Dipartimento di Scienze Farmaceutiche, Facoltà di Scienze del Farmaco, Università degli Studi di Milano, Via L. Mangiagalli 25, 20133 Milan, Italy.
Sergio
S
Romeo
International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India.
Pawan
P
Malhotra
D000953:Antigens, Protozoan / Q000235:genetics / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism / Q000469:parasitology*; D006801:Humans; D016778:Malaria, Falciparum / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics; D010455:Peptides / Q000737:chemistry / Q000494:pharmacology; D010963:Plasmodium falciparum / Q000201:enzymology* / Q000235:genetics; D017434:Protein Structure, Tertiary; D059748:Proteolysis
D000953:Antigens, Protozoan; D010455:Peptides; C480167:serine repeat antigen 5, Plasmodium falciparum
Enzyme kinetics; Peptide synthesis; Plasmodium; Site directed mutagenesis