Abstract
Most mitochondrial proteins are nuclear encoded and synthesized in the cytosol with an N-terminal mitochondrial targeting sequence or presequence for subsequent import into mitochondria. Here, we describe the proteolytic processing and inner membrane potential-dependent translocation of a dynamin family member by the Dictyostelium discoideum mitochondrial import system. Our results show that the unusual D. discoideum dynamin B presequence is removed through a processing mechanism that is common for mitochondrial matrix proteins. We identified a minimal segment of the dynamin B presequence containing seven lysine residues. This 47-residue region is, in combination with consensus matrix protease cleavage sites, necessary and sufficient for mitochondrial targeting. The correct positioning of these lysine residues plays a critical role for the proper processing and mitochondrial import of dynamin B in D. discoideum. Fluorescent proteins tagged with the dynamin B presequence or presequence regions supporting mitochondrial import in D. discoideum are imported with similar efficiency into the mitochondrial matrix of mammalian cells, indicating that the basic mechanisms underlying mitochondrial protein import are highly conserved from amoebozoa to mammalia.
Highlights
Mitochondria are endosymbiotic organelles of eubacterial origin that retain their genomic DNA [1]
We identified a short sequence within the dynamin B presequence that can serve as mitochondrial targeting sequence (MTS)
D. discoideum dynamin B is produced as preprotein with a presequence of 136 amino acid presequence that is rich in Asn (25%), Gln (8%), Ile (10%), Lys (12%), and Tyr (8%) and Ser (8%) residues
Summary
Mitochondria are endosymbiotic organelles of eubacterial origin that retain their genomic DNA [1]. Despite the presence of an independent mitochondrial genome, almost all mitochondrial proteins are encoded by nuclear genes that are translated in the cytoplasm and have to be translocated across mitochondrial membranes [2,3]. Most mitochondrial proteins contain a Nterminal presequence that serves as targeting sequence for import into the mitochondrial matrix. Transport of the preprotein into the matrix is facilitated by the translocase complexes of the mitochondrial outer (TOM) and inner (TIM) membranes [3]. Translocation depends on ATP hydrolysis and the electrochemical potential across the inner membrane (DYm). The presequence is usually proteolytically removed following import, as it might otherwise interfere with normal protein function [10,11]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
