The Kinase Domain Alters the Kinetic Properties of the Myosin IIIA Motor
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- 作者：André ; a C. Dosé ; Shobana Ananthanarayanan ; Judy E. Moore ; Amoreena C. Corsa ; Beth Burnside ; Christopher M. Yengo
- 刊名：Biochemistry
- 出版年：2008
- 出版时间：February 26, 2008
- 年：2008
- 卷：47
- 期：8
- 页码：2485 - 2496
- 全文大小：408K
- 年卷期：v.47,no.8(February 26, 2008)
- ISSN：1520-4995
文摘
Myosin IIIA is unique among myosin proteins in that it contains an N-terminal kinase domaincapable of autophosphorylating sites on the motor domain. A construct of myosin IIIA lacking the kinasedomain localizes more efficiently to the stereocilia tips and alters the morphology of the tips in inner earhair cells. Therefore, we performed a kinetic analysis of myosin IIIA without the kinase domain (MIII
K) and compared these results with our reported analysis of myosin IIIA containing the kinase domain(MIII). The steady-state kinetic properties of MIII K indicate that it has a 2-fold higher maximum actin-activated ATPase rate (kcat = 1.5 ± 0.1 s-1) and a 5-fold tighter actin affinity (KATPase = 6.0 ± 1.4 
M,and KActin = 1.4 ± 0.4 M) compared to MIII. The rate of ATP binding to the motor domain is enhancedin MIII K (K1k+2 
0.10 ± 0.01 M-1·s-1) to a level similar to the rate of binding to MIII in thepresence of actin. The rate of ATP hydrolysis in the absence of actin is slow and may be rate limiting.Actin-activated phosphate release is identical with and without the kinase domain. The transition betweenactomyosin.ADP states, which is rate limiting in MIII, is enhanced in MIII K. MIII K accumulatesmore efficiently at the tips of filopodia in HeLa cells. Our results suggest a model in which the activityand concentration of myosin IIIA localized to the tips of actin bundles mediates the morphology of thetips in sensory cells.
K) and compared these results with our reported analysis of myosin IIIA containing the kinase domain(MIII). The steady-state kinetic properties of MIII K indicate that it has a 2-fold higher maximum actin-activated ATPase rate (kcat = 1.5 ± 0.1 s-1) and a 5-fold tighter actin affinity (KATPase = 6.0 ± 1.4 M,and KActin = 1.4 ± 0.4 M) compared to MIII. The rate of ATP binding to the motor domain is enhancedin MIII K (K1k+2 0.10 ± 0.01 M-1·s-1) to a level similar to the rate of binding to MIII in thepresence of actin. The rate of ATP hydrolysis in the absence of actin is slow and may be rate limiting.Actin-activated phosphate release is identical with and without the kinase domain. The transition betweenactomyosin.ADP states, which is rate limiting in MIII, is enhanced in MIII K. MIII K accumulatesmore efficiently at the tips of filopodia in HeLa cells. Our results suggest a model in which the activityand concentration of myosin IIIA localized to the tips of actin bundles mediates the morphology of thetips in sensory cells.