Functional characterization of the N-terminal region of myosin-2.
All class 2 myosins contain an N-terminal extension of approximately 80 residues that includes an Src homology 3 (SH3)-like subdomain. To explore the functional importance of this region, which is also present in most other myosin classes, we generated truncated constructs of Dictyostelium discoideum myosin-2. Truncation at position 80 resulted in the complete loss of myosin-2 function in vivo. Actin affinity was more than 80-fold, and the rate of ADP release approximately 40-fold decreased in this mutant. In contrast, a myosin construct that lacks only the SH3-like subdomain, corresponding to residues 33-79, displayed much smaller functional defects. In complementation experiments with myosin-2 null cells, this construct rescued myosin-2-dependent processes such as cytokinesis, fruiting body formation, and sporogenesis. An 8-fold reduction in motile activity and changes of similar extent in the affinity for ADP and filamentous actin indicate the importance of the SH3-like subdomain for correct communication between the functional regions within the myosin motor domain and suggest that local perturbations in this region can play a role in modulating myosin-2 motor activity.
Fujita-Becker
Setsuko
S
Max-Planck-Institut für Medizinische Forschung, Jahnstrasse 29, 69120 Heidelberg, Germany.
Tsiavaliaris
Georgios
G
Ohkura
Reiko
R
Shimada
Takashi
T
Manstein
Dietmar J
DJ
Sutoh
Kazuo
K
D000199:Actins / Q000737:chemistry; D000244:Adenosine Diphosphate / Q000737:chemistry; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D048749:Cytokinesis; D004023:Dictyostelium / Q000378:metabolism*; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D024462:Myosin Type II / Q000737:chemistry* / Q000378:metabolism; D009218:Myosins / Q000737:chemistry; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D018909:src Homology Domains
D000199:Actins; D000244:Adenosine Diphosphate; D000251:Adenosine Triphosphatases; D024462:Myosin Type II; D009218:Myosins