The peroxisomal multifunctional protein interacts with cortical microtubules in plant cells.
BACKGROUND
The plant peroxisomal multifunctional protein (MFP) possesses up to four enzymatic activities that are involved in catalyzing different reactions of fatty acid beta-oxidation in the peroxisome matrix. In addition to these peroxisomal activities, in vitro assays revealed that rice MFP possesses microtubule- and RNA-binding activities suggesting that this protein also has important functions in the cytosol.


RESULTS
We demonstrate that MFP is an authentic microtubule-binding protein, as it localized to the cortical microtubule array in vivo, in addition to its expected targeting to the peroxisome matrix. MFP does not, however, interact with the three mitotic microtubule arrays. Microtubule co-sedimentation assays of truncated versions of MFP revealed that multiple microtubule-binding domains are present on the MFP polypeptide. This indicates that these regions function together to achieve high-affinity binding of the full-length protein. Real-time imaging of a transiently expressed green fluorescent protein-MFP chimera in living plant cells illustrated that a dynamic, spatial interaction exits between peroxisomes and cortical microtubules as peroxisomes move along actin filaments or oscillate at fixed locations.


CONCLUSIONS
Plant MFP is associated with the cortical microtubule array, in addition to its expected localization in the peroxisome. This observation, coupled with apparent interactions that frequently occur between microtubules and peroxisomes in the cell cortex, supports the hypothesis that MFP is concentrated on microtubules in order to facilitate the regulated import of MFP into peroxisomes.
Chuong
Simon D X
SD
Department of Biological Sciences, University of Calgary, Calgary, AB, T2N 1N4, Canada. chuong@wsu.edu
Park
Nam-Il
NI
Freeman
Michelle C
MC
Mullen
Robert T
RT
Muench
Douglas G
DG
D001665:Binding Sites; D049452:Green Fluorescent Proteins; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000378:metabolism*; D019697:Onions / Q000166:cytology / Q000378:metabolism; D012275:Oryza / Q000166:cytology / Q000378:metabolism; D020675:Peroxisomes / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism*
D008869:Microtubule-Associated Proteins; D009097:Multienzyme Complexes; D010940:Plant Proteins; D016601:RNA-Binding Proteins; C447611:peroxisomal multifunctional protein, Oryza sativa; D049452:Green Fluorescent Proteins