Submitted to: Biochemical Journal
Publication Type: Other
Publication Acceptance Date: 8/22/2016
Publication Date: N/A
Interpretive Summary: The proposal that mitochondrial protein abundance is related to the length and structure of the amino-terminus of the protein is critically evaluated. This information will be useful to other scientists who study soybeans and other oil-rich seeds in order to develop strategies useful for modification of seed proteins for food, feed, and industrial applications.
Technical Abstract: The human mitochondrial glutamate dehydrogenase isozymes (hGDH1 and 2) are abundant matrix-localized proteins encoded by nuclear genes. The proteins are synthesized in the cytoplasm, with an atypically long N-terminal mitochondrial targeting sequence (MTS). The results of secondary structure predictions suggest the presence of two a-helices within the N-terminal region of the MTS. Results from deletion analyses indicate that individual helices have limited ability to direct protein import and matrix localization, but that there is a synergistic interaction when both helices are present (Kalef-Ezra, E., Kotzamani, D., Zaganas, I., Katrakili, N., Plaitakis, A., and Tokatlidis, K. (2016) Import of a major mitochondrial enzyme depends on synergy between two distinct helices of its presequence. Biochemical Journal Jul 15, 2016, BCJ20160535). Mutagenesis of the MTS cleavage sites blocked post-import removal of the pre-sequences but did not impede import. The authors propose that the high matrix levels of hGDH can be attributed to the unusual length and secondary structure of the MTS.