Identification of novel subunits of the TOM complex from Arabidopsis thaliana

authored by

Wolf Werhahn, Lothar Jänsch, Hans Peter Braun

Abstract

The preprotein translocase of the outer mitochondrial membrane (also called TOM complex) from A rabidopsis thaliana was characterized by Blue-native gel electrophoresis (BN-PAGE) and Electrospray Tandem Mass Spectrometry (ESI-MS/MS). BN-PAGE allows to prepare a very stable 390 kDa complex that includes six different protein types: the 34 kDa translocation pore TOM40, the 21/23 kDa preprotein receptor TOM20, the small TOM component TOM7 and three further subunits of 10, 6.3 and 6.0 kDa. Primary structures of all TOM subunits were elucidated. The 10 kDa subunit represents a truncated version of the TOM22 preprotein receptor and the two 6 kDa proteins represent subunits possibly homologous to fungal TOM6 and TOM5, although sequence conservation is at the borderline of significance. TOM40, TOM7 and one or both of the 6 kDa subunits form a subcomplex of about 100 kDa. The six TOM proteins from A rabidopsis are encoded by 12 genes, at least 11 of which are expressed. While the subunit composition of the TOM complex from fungi, animals and plants is remarkably conserved, the domain structure of individual TOM proteins differs, e.g. acidic domains in TOM22 and the 6 kDa TOM subunits from Arabidopsis are absent. The domain structure of the Arabidopsis TOM complex does not support the so-called 'acid chain hypothesis', which explains the translocation of proteins across the outer mitochondrial membrane of mitochondria by the binding of preproteins to acidic protein domains within the TOM complex. Functional implications are discussed.

Organisation(s)

Institute of Plant Genetics

External Organisation(s)

Helmholtz Centre for Infection Research (HZI)

Type

Article

Journal

Plant physiology and biochemistry

Volume

41

Pages

407-416

No. of pages

10

ISSN

0981-9428

Publication date

23.05.2003

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Physiology, Genetics, Plant Science

Electronic version(s)

https://doi.org/10.1016/S0981-9428(03)00047-0 (Access: Unknown)