Myosin IIb is unconventionally conventional.
Members of the myosin II class of molecular motors have been referred to as "conventional," a term used to describe their ability to form thick filaments, their low duty ratio, the ability of individual motor-containing "heads" to operate independently of each other, and their rate-limiting phosphate release. These features ensure that those motors that have completed their power stroke dissociate rapidly enough to prevent them from interfering with those motors that are beginning theirs. However, in this study, we demonstrate that myosin IIB, a cytoplasmic myosin II particularly enriched in the central nervous system and cardiac tissue, has a number of features that it shares instead with "unconventional" myosin isoforms, including myosins V and VI. These include a high duty ratio, rate-limiting ADP release, and high ADP affinity. These features imply that myosin IIB serves a set of physiologic needs different from those served by its more conventional myosin II counterparts, and this work provides a plausible basis for explaining the physiologic role of this unconventionally conventional myosin.
Departments of Neurology and Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama 35294-3293, USA. stevensr@uab.edu
Steven S
SS
Rosenfeld
Jun
J
Xing
Li-Qiong
LQ
Chen
H Lee
HL
Sweeney
D000199:Actins / Q000737:chemistry / Q000494:pharmacology; D000244:Adenosine Diphosphate / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002645:Chickens; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006863:Hydrogen-Ion Concentration; D007313:Insecta; D007700:Kinetics; D008956:Models, Chemical; D024501:Nonmuscle Myosin Type IIB / Q000737:chemistry* / Q000502:physiology*; D010710:Phosphates / Q000737:chemistry; D011485:Protein Binding; D020033:Protein Isoforms; D011994:Recombinant Proteins / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D013696:Temperature
D000199:Actins; D018076:DNA, Complementary; D010710:Phosphates; D020033:Protein Isoforms; D011994:Recombinant Proteins; D000244:Adenosine Diphosphate; D024501:Nonmuscle Myosin Type IIB