Characterisation of two unc104-related kinesin motor proteins in Aspergillus nidulans

Nadine Zekert, Reinhard Fischer

Author address: 

Department of Applied Biosciences, Applied Microbiology, University of Karlsruhe, Karlsruhe, Germany


We have previously shown that in Aspergillus nidulans conventional kinesin (Kinesin-1), KinA, is required for fast hyphal growth (1) and the Kip2 family motor (Kinesin-7), KipA, for the maintenance of hyphal polarity (2). Here, we characterized UncA and UncB, two Unc-104 related motor proteins (Kinesin-3). UncA consists of 1631 amino acids and contains, in addition to the motor domain, a forkhead association domain and a PH domain. UncB in comparison is much smaller with only 671 amino acids. Homologues of those motors were shown to be required for mitochondrial motility along microtubules (MT) in Neurospora crassa (3), and for early endosome transportation in Ustilago maydis (4). Whereas deletion of uncB did not show any phenotype, deletion of uncA caused slower hyphal growth and a defect in hyphal polarity at higher temperature, suggesting a role in hyphal growth. UncA tagged with GFP was found in several spots in the cytoplasm, and showed rapid bidirectional movement along MT. The introduction of a point mutation at the ATPase site of the UncA motor domain inhibited its movement and caused binding of the motor to only one microtubule. UncB tagged with GFP localized to nuclei and septa at certain times and travelled from nuclei to septa along MTs. The introduction of a rigor point mutation at the ATPase site of the UncB motor domain inhibited its movement and showed accumulation of the protein in nuclei. These results suggest other functions for UncB than UncA, although creating an uncA uncB double deletion strain showed the same phenotype as an uncA-deletion strain. One important outcome of our analysis is that UncA apparently defines a certain class of MTs in the cells. 1 Requena, N., Alberti-Segui, C., Winzenburg, E., Horn, C., Schliwa, M., Philippsen, P., Liese, R. & Fischer, R. (2001). Mol. Microbiol. 42, 121-132, 2 Enke, C., Zekert, N., Veith, D. & Fischer, R. (2007). Eukaryot. Cell 6, 555-562, 3 Fuchs, F. & Westermann, B. (2005). Mol. Biol. Cell 16, 153-161, 4 Wedlich-Söldner, R., Straube, A., Friedrich, M.W. & Steinberg, G. (2002). EMBO J. 21, 2946-2957.

abstract No: 


Full conference title: 

    • ECFG 9th (2008)