Myosin I mutants with only 1% of wild-type actin-activated MgATPase activity retain essential in vivo function(s)
- Xiong Liu*,†,
- Nir Osherov†,‡,
- Roxanne Yamashita‡,
- Hanna Brzeska*,
- Edward D. Korn*,§, and
- Gregory S. May‡
- *Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Building 50, Room 2517, Bethesda, MD 20892; and ‡Division of Pathology and Laboratory Medicine, Box 54, University of Texas, M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030
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Contributed by Edward D. Korn
Abstract
The single class I myosin (MYOA) of Aspergillus nidulans is essential for hyphal growth. It is generally assumed that the functions of all myosins depend on their actin-activated MgATPase activity. Here we show that MYOA mutants with no more than 1% of the actin-activated MgATPase activity of wild-type MYOA in vitro and no detectable in vitro motility activity can support fungal cell growth, albeit with a delay in germination time and a reduction in hyphal elongation. From these and other data, we conclude that the essential role(s) of myosin I in A. nidulans is probably structural, requiring little, if any, actin-activated MgATPase or motor activity, which have long been considered the defining characteristics of the myosin family.
