A voltage-gated pore for translocation of tRNA.
Biochem Biophys Res Commun
; 439(1): 23-9, 2013 Sep 13.
Article
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| MEDLINE
| ID: mdl-23958303
ABSTRACT
Very little is known about how nucleic acids are translocated across membranes. The multi-subunit RNA Import Complex (RIC) from mitochondria of the kinetoplastid protozoon Leishmania tropica induces translocation of tRNAs across artificial or natural membranes, but the nature of the translocation pore remains unknown. We show that subunits RIC6 and RIC9 assemble on the membrane in presence of subunit RIC4A to form complex R3. Atomic Force Microscopy of R3 revealed particles with an asymmetric surface groove of â¼20 nm rim diameter and â¼1 nm depth. R3 induced translocation of tRNA into liposomes when the pH of the medium was lowered to â¼6 in the absence of ATP. R3-mediated tRNA translocation could also be induced at neutral pH by a K(+) diffusion potential with an optimum of 60-70 mV. Point mutations in the Cys2-His2 Fe-binding motif of RIC6, which is homologous to the respiratory Complex III Fe-S protein, abrogated import induced by low pH but not by K(+) diffusion potential. These results indicate that the R3 complex forms a pore that is gated by a proton-generated membrane potential and that the Fe-S binding region of RIC6 has a role in proton translocation. The tRNA import complex of L. tropica thus contains a novel macromolecular channel distinct from the mitochondrial protein import pore that is apparently involved in tRNA import in some species.
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Banco de datos:
MEDLINE
Asunto principal:
Leishmania tropica
/
ARN de Transferencia
/
Transporte de ARN
/
Potencial de la Membrana Mitocondrial
Idioma:
En
Revista:
Biochem Biophys Res Commun
Año:
2013
Tipo del documento:
Article
País de afiliación:
India