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Polypeptide release factors and stop codon recognition in the apicoplast and mitochondrion of Plasmodium falciparum
Author(s) -
Vaishya Suniti,
Kumar Vikash,
Gupta Ankit,
Siddiqi Mohammad Imran,
Habib Saman
Publication year - 2016
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.13369
Subject(s) - biology , apicoplast , genetics , start codon , stop codon , orfs , open reading frame , codon usage bias , mitochondrion , plasmodium falciparum , release factor , microbiology and biotechnology , transfer rna , peptide sequence , gene , plastid , rna , messenger rna , genome , chloroplast , malaria , immunology
Summary Correct termination of protein synthesis would be a critical step in translation of organellar open reading frames (ORFs) of the apicoplast and mitochondrion of the malaria parasite. We identify release factors (RFs) responsible for recognition of the UAA and UGA stop‐codons of apicoplast ORFs and the sole UAA stop‐codon that terminates translation from the three mitochondrial ORFs. A single nuclear‐encoded canonical RF2, Pf RF2 Api , localizes to the apicoplast. It has a conserved tripeptide motif (SPF) for stop‐codon recognition and is sufficient for peptidyl‐tRNA hydrolysis (PTH) from both UAA and UGA. Two RF family proteins are targeted to the parasite mitochondrion; a canonical RF1, Pf RF1 Mit , with a variant codon‐recognition motif (PxN instead of the conserved RF1 PxT) is the major peptidyl‐hydrolase with specific recognition of the UAA codon relevant to mitochondrial ORFs. Mutation of the N residue of the Pf RF1 Mit PxN motif and two other conserved residues of the codon recognition domain lowers PTH activity from pre‐termination ribosomes indicating their role in codon‐recognition. The second RF imported by the mitochondrion is the non‐canonical Pf ICT1 that functions as a dimer and mediates codon nonspecific peptide release. Our results help delineate a critical step in organellar translation in Plasmodium , which is an important target for anti‐malarials.