Researcher:
Keskin, Abdurrahman

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Abdurrahman

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Keskin

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Keskin, Abdurrahman

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2017 - 20184

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Researcher Of Publications: search.filters.isAuthorOfPublication.a7672296-9356-4c1c-a95b-0720229498ae

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    Deep mutational scanning reveals characteristics important for mitochondrial targeting of a tail-anchored protein.
    (The American Society for Cell Biology, 2017) N/A; N/A; N/A; Department of Molecular Biology and Genetics; Keskin, Abdurrahman; Akdoğan, Emel; Dunn, Cory David; Master Student; Master Student; Other; Department of Molecular Biology and Genetics; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A
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    Evidence for amino acid snorkeling from a high-resolution, in vivo analysis of FIS1 tail-anchor insertion at the mitochondrial outer membrane
    (Genetics Society America, 2017) N/A; N/A; N/A; Department of Molecular Biology and Genetics; Keskin, Abdurrahman; Akdoğan, Emel; Dunn, Cory David; Master Student; Master Student; Other; Department of Molecular Biology and Genetics; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A
    Proteins localized to mitochondria by a carboxyl-terminal tail anchor (TA) play roles in apoptosis, mitochondrial dynamics, and mitochondrial protein import. To reveal characteristics of TAs that may be important for mitochondrial targeting, we focused our attention upon the TA of the Saccharomyces cerevisiae Fis1 protein. Specifically, we generated a library of Fis1p TA variants fused to the Gal4 transcription factor, then, using next-generation sequencing, revealed which Fis1p TA mutations inhibited membrane insertion and allowed Gal4p activity in the nucleus. Prompted by our global analysis, we subsequently analyzed the ability of individual Fis1p TA mutants to localize to mitochondria. Our findings suggest that the membrane-associated domain of the Fis1p TA may be bipartite in nature, and we encountered evidence that the positively charged patch at the carboxyl terminus of Fis1p is required for both membrane insertion and organelle specificity. Furthermore, lengthening or shortening of the Fis1p TA by up to three amino acids did not inhibit mitochondrial targeting, arguing against a model in which TA length directs insertion of TAs to distinct organelles. Most importantly, positively charged residues were more acceptable at several positions within the membrane-associated domain of the Fis1p TA than negatively charged residues. These findings, emerging from the first high-resolution analysis of an organelle targeting sequence by deep mutational scanning, provide strong, in vivo evidence that lysine and arginine can "snorkel," or become stably incorporated within a lipid bilayer by placing terminal charges of their side chains at the membrane interface.
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    A bacteria-derived tail anchor localizes to peroxisomes in yeast and mammalian cells
    (Nature Publishing Group (NPG), 2018) Seferoğlu, Ayşe Bengisu; Department of Molecular Biology and Genetics; Dunn, Cory David; Keskin, Abdurrahman; Akdoğan, Emel; Lutfullahoglu-Bal, Guleycan; Department of Molecular Biology and Genetics; College of Sciences
    Prokaryotes can provide new genetic information to eukaryotes by horizontal gene transfer (HGT), and such transfers are likely to have been particularly consequential in the era of eukaryogenesis. Since eukaryotes are highly compartmentalized, it is worthwhile to consider the mechanisms by which newly transferred proteins might reach diverse organellar destinations. Toward this goal, we have focused our attention upon the behavior of bacteria-derived tail anchors (TAs) expressed in the eukaryote Saccharomyces cerevisiae. In this study, we report that a predicted membrane-associated domain of the Escherichia coli YgiM protein is specifically trafficked to peroxisomes in budding yeast, can be found at a pre-peroxisomal compartment (PPC) upon disruption of peroxisomal biogenesis, and can functionally replace an endogenous, peroxisome-directed TA. Furthermore, the YgiM(TA) can localize to peroxisomes in mammalian cells. Since the YgiM(TA) plays no endogenous role in peroxisomal function or assembly, this domain is likely to serve as an excellent tool allowing further illumination of the mechanisms by which TAs can travel to peroxisomes. Moreover, our findings emphasize the ease with which bacteria-derived sequences might target to organelles in eukaryotic cells following HGT, and we discuss the importance of flexible recognition of organelle targeting information during and after eukaryogenesis.
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    PublicationOpen Access
    Bacterial tail anchors can target to the mitochondrial outer membrane
    (BioMed Central, 2017) Department of Molecular Biology and Genetics; Lutfullahoglu-Bal, Guleycan; Keskin, Abdurrahman; Seferoğlu, Ayşe Bengisu; Dunn, Cory David; PhD Student; Faculty Member; Department of Molecular Biology and Genetics; Graduate School of Sciences and Engineering; College of Sciences
    Background: During the generation and evolution of the eukaryotic cell, a proteobacterial endosymbiont was re-fashioned into the mitochondrion, an organelle that appears to have been present in the ancestor of all present-day eukaryotes. Mitochondria harbor proteomes derived from coding information located both inside and outside the organelle, and the rate-limiting step toward the formation of eukaryotic cells may have been development of an import apparatus allowing protein entry to mitochondria. Currently, a widely conserved translocon allows proteins to pass from the cytosol into mitochondria, but how proteins encoded outside of mitochondria were first directed to these organelles at the dawn of eukaryogenesis is not clear. Because several proteins targeted by a carboxyl-terminal tail anchor (TA) appear to have the ability to insert spontaneously into the mitochondrial outer membrane (OM), it is possible that self-inserting, tail-anchored polypeptides obtained from bacteria might have formed the first gate allowing proteins to access mitochondria from the cytosol. Results: Here, we tested whether bacterial TAs are capable of targeting to mitochondria. In a survey of proteins encoded by the proteobacterium Escherichia coli, predicted TA sequences were directed to specific subcellular locations within the yeast Saccharomyces cerevisiae. Importantly, TAs obtained from DUF883 family members ElaB and YqjD were abundantly localized to and inserted at the mitochondrial OM. Conclusions: Our results support the notion that eukaryotic cells are able to utilize membrane-targeting signals present in bacterial proteins obtained by lateral gene transfer, and our findings make plausible a model in which mitochondrial protein translocation was first driven by tail-anchored proteins.