Synopsis of Current Research Interests - Plastid Rhomboid Proteins
Our past research on the Tic40 translocon component helped unveil new insights into plastid protein transport mechanisms and that the process is dynamic. These insights eventually led us to the discovery that there is a potential link between Tic40 and plastid rhomboid proteins. Rhomboid proteins are widespread and are part of the regulated intramembrane proteolysis mechanism for controlling processes such as development, signaling, bacterial protein transport, stress response/adaptation in the endoplasmic reticulum, lipid metabolism, and mitochondrial membrane remodeling, to name a few. Our discovery of the Tic40-rhomboid link forms a knowledge platform for investigating regulatory and developmental aspects of plastids. The focus of our current research is on the following aspects: 1) the roles of plastid rhomboid proteins in plant development, plastid biogenesis and protein transport; 2) the roles played by inactive forms and alternative splice variants of plastid rhomboid proteins, and 3) the possible interactions between plastid rhomboid proteins and cellular processes such cell cycle and stress adaptation.
Recent Poster Presented for the Above Research at Recent Conferences and Meetings
1) Plastid rhomboid proteins: The emerging picture - Presented by Joshua Powles at the 2012-2013 Cell and Molecular Research Lecture Series, Queen's University, Kingston, Ontario, Canada (February 2013).
2) Do plastid rhomboid proteases bind divalent metal ions? - Presented by Reem Abaza at the 2012-2013 Undergraduate Thesis Seminar Series, Queen's University, Kingston, Ontario, Canada (November 2012).
3) Characterizing an "inactive" organellar rhomboid protein in Arabidopsis - Presented by Joshua Powles at the 15th Annual Scientific Meeting for Health Sciences Research Trainees. Kingston, Ontario, Canada. (May 2012) (The work presented in this poster was published as part of a research paper in the journal Botany (Sedivy-Haley K, Powles J, Newcomb W, Ko K. 2011. Molecular characterization of organellar rhomboid proteins in Arabidopsis . Botany 89: 873-885.).
4)Analyzing rhomboid protease activity using site-directed mutagenesis? - Presented by Eric Chapman at the 2011-2012 Undergraduate Thesis Seminar Series, Queen's University, Kingston, Ontario, Canada (November 2011). Awarded "Best Seminar" prize.
5) Is there alternative splicing in the At1g18600 mitochondrial rhomboid gene system? - Presented by Elizabeth Behariell at the 2010-2011 Undergraduate Thesis Seminar Series, Queen's University, Kingston, Ontario, Canada (November 2010).
Selection of Relevant Publications
Powles J, Sedivy-Haley K, Chapman E, Ko K. 2013. Characterization of three alternative splice variants associated with the Arabidopsis rhomboid protein gene At1g74130. Botany 91: 840-849.
Sedivy -Haley K, Powles J, Ko K. 2012. Characterization of two alternative splice variants associated with the Arabidopsis rhomboid protein gene At1g25290. Botany 90: 1252-1262.
Sedivy -Haley K, Powles J, Newcomb W, Ko K. 2011. Molecular characterization of organellar rhomboid proteins in Arabidopsis . Botany 89: 873-885.
Powles J, Savage P, Wu E, Karakasis K, Ko K. 2011. Motif-based evidence that a plastid translocon component acts like a rhomboid protease substrate in yeast mitochondria. Botany 89: 499-511.
Karakasis, K., Taylor, D., Ko. K. 2007. Uncovering a potential link between a plastid translocon component and rhomboid proteases using yeast mitochondria-based assays. Plant Cell Physiol. 48: 655-661.
Ko, K., Chan, K., Karakasis, K., Pedram, B. 2006. Plastid protein import: Coping with diversity. Invited Review. Can. J. Bot. 84: 543-550.
Ko , K., Taylor, D., Argenton , P., Innes, J., Pedram , B., Siebert, F., Granell , A, Ko , Z. 2005. Evidence that the plastid translocon Tic40 components possess modulating capabilities. J. Biol. Chem. 280: 215-224.
Labate , M.T.V., Ko , K., Ko , Z.W., Costa Pinto, L.S.R., Real, M.J.U.D., Romano, M.R., Barja , P.R., Granell , A., Friso , G., van Wijk , K.J., Brugnoli , E., Augusti , A., Labate , C.A. 2004. Constitutive expression of pea Lhcb1-2 in tobacco affects plant development, morphology and photosynthetic capacity. Plant Mol. Biol. 55: 702-714.
Ko, K., Banerjee, S., Innes, J., Taylor, D., Ko, Z. 2004. The Tic40 translocon components exhibit preferential interactions with different forms of the Oee1 plastid protein precursor. Functional Plant Biol. 31: 285-294.
Taylor, D., Bedard , J., Ko , K. 2004. A cross-organelle proteomic approach for elucidating plastid translocon function. Proceedings of the XIIth International Congress: Genes, Gene Families, and Isozymes . CD-ROM Publication January 2004. Pages 93-97.
Ko , K., Banerjee , S., Innes, J., Granell , A., Taylor , D., Ko , Z. 2004. Profiling preferential interactions between plastid translocon components and different forms of a protein precursor using a bacterial proteomic approach. Proceedings of the XIIth International Congress: Genes, Gene Families, and Isozymes . CD-ROM Publication January 2004. Pages 99-104.
Gordon, B., Ko , K. 2002. The plastid protein import machinery component Toc36 exhibits an affinity for the bacterial protein translocation process. Arch. Biochem . Biophys . 404:147-157.
Ko , K., Ko , Z. 1999. In vitro targeting of the Toc36 component of the chloroplast envelope protein import apparatus involves a complex set of signals. Biochim . Biophys . Acta . 1421: 198-206.
Pang, P., Meathrel , K., Ko, K. 1997. A component of the chloroplast protein import apparatus functions in bacteria. J. Biol. Chem. 272: 25623-25627.
Kourtz , L., K. Ko. 1997. The early stage of chloroplast protein import involves Com70. J. Biol. Chem. 272: 2808-2813.
Schnell, D.J., Blobel , G., Keegstra , K., Kessler, F., Ko, K., Soll, J. 1997. Nomenclature for the protein import components of the chloroplast envelope. Trends in Cell Biol. 7:303-304
Wan, J., Blakeley, S., Dennis, D.T. , Ko, K. 1996. Transit peptides play a major role in the preferential import of proteins into chloroplasts and leucoplasts. J. Biol. Chem. 271: 31227-31233.
Ko, K., Budd, D., Wu, C., Seibert, F., Kourtz, L., Ko. Z.W. 1995. Isolation and characterization of a cDNA clone encoding a member of the Com44/Cim44 envelope components of the chloroplast protein import apparatus. J. Biol. Chem. 270: 28601-28608.
Wan, J., Blakeley, S.,Dennis, D.T., Ko, K. 1995. Import characteristics of a leucoplast pyruvate kinase are influenced by a 19 amino acid domain within the protein. J. Biol. Chem. 270: 16731-16739.
Wu, C., Seibert, F., Ko, K. 1994. Identification of chloroplast envelope proteins in close physical proximity to a partially translocated chimeric precursor protein. J. Biol. Chem. 269: 32264-32271.
Wu, C., Ko, K. 1993. Identification of an uncleavable targeting signal in the 70-kilodalton spinach chloroplast outer envelope membrane protein. J. Biol. Chem. 268: 19384-19391.
Ko, K., Bornemisza, O., Kourtz, L. , Ko, Z.W., Plaxton, W.C., Cashmore, A.R.. 1992. Isolation and characterization of a cDNA clone for a cognate 70 kDa heat shock protein associated with the chloroplast envelope. J. Biol. Chem. 267:2986-2993.
Ko, K., Ko, Z.W. 1992. Carboxyl-terminal sequences can influence the In vitro import and intra-organellar targeting of chloroplast protein precursors. J. Biol. Chem. 267:13910-13916.
Ko, K., Cashmore, A.R. 1989. Targeting of proteins to the thylakoid lumen by the bipartite transit peptide of the 33 kD oxygen-evolving protein. EMBO J. 8:3187-3194.