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Journal of Bacteriology, February 2007, p. 844-850, Vol. 189, No. 3
0021-9193/07/$08.00+0     doi:10.1128/JB.01261-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

A Protein from a Parasitic Microorganism, Rickettsia prowazekii, Can Cleave the Signal Sequences of Proteins Targeting Mitochondria{triangledown} ,{dagger}

Sakae Kitada,1* Tsuneo Uchiyama,2 Tomoyuki Funatsu,1 Yumiko Kitada,1 Tadashi Ogishima,1 and Akio Ito1

Department of Chemistry, Faculty of Science, Kyushu University, Fukuoka 812-8581, Japan,1 Department of Virology, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima 770-8503, Japan2

Received 10 August 2006/ Accepted 19 November 2006

The obligate intracellular parasitic bacteria rickettsiae are more closely related to mitochondria than any other microbes investigated to date. A rickettsial putative peptidase (RPP) was found to resemble the {alpha} and ß subunits of mitochondrial processing peptidase (MPP), which cleaves the transport signal sequences of mitochondrial preproteins. RPP showed completely conserved zinc-binding and catalytic residues compared with ß-MPP but barely contained any of the glycine-rich loop region characteristic of {alpha}-MPP. When the biochemical activity of RPP purified from a recombinant source was analyzed, RPP specifically hydrolyzed basic peptides and presequence peptides with frequent cleavage at their MPP-processing sites. Moreover, RPP appeared to activate yeast ß-MPP so that it processed preproteins with shorter presequences. Thus, RPP behaves as a bifunctional protein that could act as a basic peptide peptidase and a somewhat regulatory protein for other protein activities in rickettsiae. These are the first biological and enzymological studies to report that a protein from a parasitic microorganism can cleave the signal sequences of proteins targeted to mitochondria.

* Corresponding author. Mailing address: Department of Chemistry, Faculty of Science, Kyushu University, Fukuoka 812-8581, Japan. Phone: 81-92-642-4182. Fax: 81-92-642-2607. E-mail: s.kitscc{at}mbox.nc.kyushu-u.ac.jp.

{triangledown} Published ahead of print on 8 December 2006.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

Journal of Bacteriology, February 2007, p. 844-850, Vol. 189, No. 3
0021-9193/07/$08.00+0     doi:10.1128/JB.01261-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.





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