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Structural requirements for in vivo myosin I function in Aspergillus nidulans
N Osherov1, R A Yamashita, Y S Chung
1Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
Abstract:
We have investigated the minimal requirements of the tail region for myosin I function in vivo using the filamentous fungus Aspergillus nidulans. The CL3 strain (McGoldrick, C. A., Gruver, C., and May, G. S. (1995) J. Cell Biol. 128, 577-587) was transformed with a variety of myoA constructs containing mutations in the IQ, TH-1-like, SH3, and proline-rich domains by frameshift or in-frame deletions of the tail domains. The resulting strains contained wild type myoA driven by the alcA promoter and a mutant myoA driven by its endogenous promoter. This strategy allowed for selective expression of the wild type and/or mutant form of MYOA by the choice of growth medium. Proper septation and hyphal branching were found to be dependent on the interaction of the IQ motifs with calmodulin, as well as, the presence of its proline-rich domain. Additionally, a single proline-rich motif was sufficient for nearly wild type MYOA function. Most surprisingly, the SH3 domain was not essential for MYOA function. These studies expand our previous knowledge of the function of MYOA to include roles in hyphal morphogenesis, septal wall formation, and cell polarity, laying the groundwork for more detailed investigations on the function of the various tail domains in MYOA.
Insights
Myosin I tail domains are crucial for fungal cell functions. Specific interactions, like IQ motifs with calmodulin and proline-rich domains, are essential for proper septation and hyphal branching in Aspergillus nidulans.
Area of Science:
- Cell Biology
- Mycology
- Molecular Genetics
Background:
- Myosin I is a motor protein involved in various cellular processes.
- The tail region of myosin I contains several domains (IQ, TH-1-like, SH3, proline-rich) that mediate interactions with other proteins and regulate function.
- Understanding the specific roles of these tail domains is crucial for elucidating myosin I function in vivo.
Purpose of the Study:
- To investigate the minimal requirements of the myosin I tail region for its function in vivo.
- To determine the essential domains and interactions within the myosin I tail for proper cellular processes in Aspergillus nidulans.
Main Methods:
- Utilized the filamentous fungus Aspergillus nidulans for in vivo studies.
- Generated myoA constructs with mutations (frameshift or deletions) in IQ, TH-1-like, SH3, and proline-rich domains.
- Employed a dual-promoter system (alcA and endogenous) for selective expression of wild-type and mutant MYOA.
Main Results:
- Proper septation and hyphal branching depend on the interaction of IQ motifs with calmodulin and the presence of proline-rich domains.
- A single proline-rich motif was sufficient for near wild-type MYOA function.
- The SH3 domain was found not to be essential for MYOA function in this context.
Conclusions:
- The tail region of myosin I plays critical roles in hyphal morphogenesis, septal wall formation, and cell polarity.
- Specific domain interactions within the myosin I tail are essential for its in vivo function.
- These findings provide a foundation for further detailed investigations into the functional significance of individual myosin I tail domains.