A structural investigation of complex I and I + III2 supercomplex from Zea mays at 11-13 Å resolution

Assignment of the carbonic anhydrase domain and evidence for structural heterogeneity within complex I

authored by
Katrin Peters, Natalya V. Dudkina, Lothar Jänsch, Hans Peter Braun, Egbert J. Boekema

The projection structures of complex I and the I + III2 supercomplex from the C4 plant Zea mays were determined by electron microscopy and single particle image analysis to a resolution of up to 11 Å. Maize complex I has a typical L-shape. Additionally, it has a large hydrophilic extra-domain attached to the centre of the membrane arm on its matrix-exposed side, which previously was described for Arabidopsis and which was reported to include carbonic anhydrase subunits. A comparison with the X-ray structure of homotrimeric γ-carbonic anhydrase from the archaebacterium Methanosarcina thermophila indicates that this domain is also composed of a trimer. Mass spectrometry analyses allowed to identify two different carbonic anhydrase isoforms, suggesting that the γ-carbonic anhydrase domain of maize complex I most likely is a heterotrimer. Statistical analysis indicates that the maize complex I structure is heterogeneous: a less-abundant "type II" particle has a 15 Å shorter membrane arm and an additional small protrusion on the intermembrane-side of the membrane arm if compared to the more abundant "type I" particle. The I + III2 supercomplex was found to be a rigid structure which did not break down into subcomplexes at the interface between the hydrophilic and the hydrophobic arms of complex I. The complex I moiety of the supercomplex appears to be only of "type I". This would mean that the "type II" particles are not involved in the supercomplex formation and, hence, could have a different physiological role.

Institute of Plant Genetics
External Organisation(s)
University of Groningen
Helmholtz Centre for Infection Research (HZI)
Biochimica et Biophysica Acta - Bioenergetics
No. of pages
Publication date
Publication status
Peer reviewed
ASJC Scopus subject areas
Biophysics, Biochemistry, Cell Biology
Electronic version(s)
https://doi.org/10.1016/j.bbabio.2007.10.012 (Access: Open)