Paris Z, Changmai P, Rubio MA, Zikova A, Stuart KD, Alfonzo JD, Lukes J.
Department
of Microbiology, Ohio State University Biochemistry Program and The
Center for RNA Biology, The Ohio State University, Columbus, OH
43210-1292, USA. Seattle
Biomedical Research Institute, Seattle, Washington, USA. Biology
Centre, Institute of Parasitology, Czech Academy of Sciences, 37005
Ceské Budejovice (Budweis), Czech Republic.
Fe/S clusters are part of the active site of many enzymes and are
essential for cell viability. In eukaryotes the cysteine desulfurase Nfs
(IscS) donates the sulfur during Fe/S cluster assembly and was thought
sufficient for this reaction. Moreover, Nfs is indispensable for tRNA
thiolation, a modification generally required for tRNA function and
protein synthesis. Recently, Isd11 was discovered as an integral part of
the Nfs activity at an early step of Fe/S cluster assembly. Here we
show, using a combination of genetic, molecular and biochemical
approaches, that Isd11, in line with its strong association with Nfs, is
localized in the mitochondrion of T. brucei. In addition to its
involvement in Fe/S assembly, Isd11 also partakes in both cytoplasmic
and mitochondrial tRNA thiolation, whereas Mtu1, another protein
proposed to collaborate with Nfs in tRNA thiolation, is required for
this process solely within the mitochondrion. Taken together these data
places Isd11 at the center of these sulfur transactions and raises the
possibility of a connection between Fe/S metabolism and protein
synthesis, helping integrate two seemingly unrelated pathways.
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