Chloroquine Inhibits Heme-Dependent Protein Synthesis in Plasmodium falciparum

Surolia, Namita and Padmanaban, Govindarajan (1991) Chloroquine Inhibits Heme-Dependent Protein Synthesis in Plasmodium falciparum. In: PNAS, 88 (11). pp. 4786-4790.

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Abstract

A cell-free protein-synthesizing system has been reconstituted using the S-30 fraction or ribosomes and the S-100 fraction from Plasmodium falciparum. Addition of heme in vitro stimulates cell-free protein synthesis strikingly. Chloroquine inhibits the heme-dependent protein synthesis in the parasite lysate. The drug has also been found to inhibit parasite protein synthesis in situ at therapeutic concentrations soon after addition to parasite cultures. Ribosomes as well as the S-100 fraction isolated from such chloroquine-treated cultures are defective in protein synthesis. Addition of hemin plus glucose 6-phosphate or high concentrations of GTP, cAMP, and an active preparation of eIF-2 to the parasite cell-free system restores protein synthesis to a significant extent in chloroquine-treated cultures. Under conditions of inhibition of protein synthesis in situ by chloroquine in the culture, the parasite eukaryotic initiation factor 2-alpha- (eIF-2-alpha) is phosphorylated in the parasite lysate to a greater extent than that observed in the control culture. Addition of hemin in vitro suppresses this phosphorylation. eIF-2-alpha kinase activity is present in the parasite lysate and is not a contaminant derived from the human erythrocytes used to culture the parasite. The heme-chloroquine interactive effects can also be demonstrated with purified eIF-2-alpha kinase from rabbit reticulocyte lysate. It is proposed that chloroquine inhibits heme-dependent protein synthesis in the parasite and this is an early event mediating the growth-inhibitory effects of the drug.

Item Type:	Journal Article
Publication:	PNAS
Publisher:	National Academy of Sciences
Additional Information:	Copyright of this article belongs to National Academy of Sciences.
Keywords:	Malaria Parasite;Cell-Free System;Translation;Protein Synthesis Insitu;Eukaryotic Initiation Factor-2-Alpha Kinase.
Department/Centre:	Division of Biological Sciences > Biochemistry Division of Biological Sciences > Molecular Reproduction, Development & Genetics
Date Deposited:	16 Nov 2010 06:33
Last Modified:	16 Nov 2010 06:33
URI:	http://eprints.iisc.ac.in/id/eprint/33699

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