Laboratory of Organelle Biology


Associate Professor
Masato NAKAI
mail nakai @

Plant Science


Institute for Protein Research



Research Theme

We have been studying molecular mechanisms and evolution of chloroplast biogenesis in higher plants and various algae with techniques of biochemistry, genetics, and cell biology. Our current main topics are: i) Elucidation of molecular mechanisms of protein translocation across the envelope membranes of chloroplasts. ii) Molecular evolutionary studies on the chloroplast protein import system. If you would like to join our laboratory, please contact us in the first instance.

Elucidation of molecular mechanisms and molecular evolution of chloroplast protein import system.

In plants and algae, the eukaryotes, photosynthesis is carried out in a specialized organelle called chloroplast. It is now widely accepted that virtually all chloroplasts in today’s photosynthetic eukaryotes derive from one fairly rare primary endosymbiotic event with a cyanobacterium-like ancestor thought to have occurred more than a billion years ago. In the course of evolution, massive transfer of genes from the endosymbiont to the host’s nuclear genome occurred, accompanied with the development of the protein transport system that allows these nuclear-encoded chloroplast proteins back into the endosymbiont. Extant higher plants can synthesize only ~100 proteins inside the chloroplast but must import such 2000-3000 different cytosolically-synthesized nuclear-encoded proteins, across the double envelope membranes surrounding this organelle, to fulfill their complex physiological roles including photosynthetic functions. Two successive protein translocons at the outer and inner envelope membranes, termed TOC and TIC, respectively, are responsible for the task of protein import into chloroplasts. Our recent discovery of the genuine TIC translocon (Science, 2013)which are well conserved among most land plants as well as green algae could provide us an entirely revised view on the molecular mechanisms of protein translocation across the inner envelope membrane of chloroplasts and also novel insights on the evolution of the chloroplast protein import system.

0Evolution of the protein import system that allows the nuclear-encoded chloroplast proteins back into the organelle.


Kikuchi S, Asakura Y, Imai M, Nakahira Y, Kotani Y, Hashiguchi Y, Nakai Y, Takafuji K, Bédard J, Hirabayashi-Ishioka Y, Mori H, Shiina T, Nakai M. A Ycf2-FtsHi heteromeric AAA-ATPase complex is required for chloroplast protein import. Plant Cell (BREAKTHROUGH REPORT) 30(11) (OPEN ACCESS)) , 2677 - 2703 (2018)

Nakai M. New Perspectives on Chloroplast Protein Import. (REVIEW) Plant Cell Physiol. 59(6) , 1111 - 1119 (2018)

Nakai M. (Review) The TIC complex uncovered: The alternative view on the molecular mechanism of protein translocation across the inner envelope membrane of chloroplasts. Biochim Biophys Acta 1847(9) , 957 - 967 (2015)

Nakai M. (Commentary) YCF1: A Green TIC Plant Cell 27(7) , 1834 - 1838 (2015)

Kikuchi S, Bédard J, Hirano M, Hirabayashi Y, Oishi M, Imai M, Takase M, Ide T, Nakai M. Uncovering the Protein Translocon at the Chloroplast Inner Envelope Membrane Science 339(6119) , 571 - 574 (2013)

Hirabayashi Y, Kikuchi S, Oishi M, Nakai M. In vivo studies on the roles of two closely related Arabidopsis Tic20 proteins, AtTic20-I and AtTic20-IV. Plant Cell Physiol. 52(3) , 469 - 478 (2011)

Kikuchi S, Oishi M, Hirabayashi Y, Lee DW, Hwang I, Nakai M. A 1-Megadalton Translocation Complex Containing Tic20 and Tic21 Mediates Chloroplast Protein Import at the Inner Envelope Membrane. Plant Cell 21(6) , 1781 - 1797 (2009)

Yabe T, Morimoto K, Kikuchi S, Nishio K, Terashima I, Nakai M. The Arabidopsis Chloroplastic NifU-Like Protein AtCnfU, Which Can Act as an Iron-Sulfur Cluster Scaffold Protein, Is Required for Biogenesis of Ferredoxin and Photosystem I. Plant Cell 16(4) , 993 - 1007 (2004)

Asakura Y, Hirohashi T, Kikuchi S, Belcher S, Osborne E, Yano S, Terashima I, Barkan A, Nakai M. Maize Mutants Lacking Chloroplast FtsY Exhibit Pleiotropic Defects in the Biogenesis of Thylakoid Membranes. Plant Cell 16(1) , 201 - 214 (2004)


Institute for Protein Research
Osaka University
3-2 Yamadaoka, Suita
Osaka 565-0871, JAPAN
Tel: +81-6-6879-8612
Fax: +81-6-6879-8613