The regulatory domain of the myosin head behaves as a rigid lever.
نویسندگان
چکیده
The regulatory domain of the myosin head is believed to serve as a lever arm that amplifies force generated in the catalytic domain and transmits this strain to the thick filament. The lever arm itself either can be passive or may have a more active role storing some of the energy created by hydrolysis of ATP. A structural correlate which might distinguish between these two possibilities (a passive or an active role) is the stiffness of the domain in question. To this effect we have examined the motion of the proximal (ELC) and distal (RLC) subdomains of the regulatory domain in reconstituted myosin filaments. Each subdomain was labeled with a spin label at a unique cysteine residue, Cys-136 of ELC or Cys-154 of mutant RLC, and its mobility was determined using saturation transfer electron paramagnetic resonance spectroscopy. The mobility of the two domains was similar; the effective correlation time (tau(eff)) for ELC was 17 micros and that for RLC was 22 micros. Additionally, following a 2-fold change of the global dynamics of the myosin head, effected by decreasing the interactions with the filament surface (or the other myosin head), the coupling of the intradomain dynamics remained unchanged. These data suggest that the regulatory domain of the myosin head acts as a single mechanically rigid body, consistent with the regulatory domain serving as a passive lever.
منابع مشابه
Independent mobility of catalytic and regulatory domains of myosin heads.
The recent determination of the myosin head atomic structure has led to a new model of muscle contraction, according to which mechanical torque is generated in the catalytic domain and amplified by the lever arm made of the regulatory domain [Fisher, A. J., Smith, C. A., Thoden, J., Smith, R., Sutoh, K., Holden, H. M. & Rayment, I. (1995) Biochemistry 34, 8960-8972]. A crucial aspect of this mo...
متن کاملEssential "ankle" in the myosin lever arm.
C ellular motors are fascinating machines that function by undergoing successive conformational changes that require joints in their structure. Where these are located is particularly critical for molecular motors that produce force with relatively rigid lever arms, such as myosins (1). A long-standing paradox in myosin function may finally be understood from structural insights provided by Coh...
متن کاملConformational selection during weak binding at the actin and myosin interface.
The molecular mechanism of the powerstroke in muscle is examined by resonance energy transfer techniques. Recent models suggesting a pre-cocking of the myosin head involving an enormous rotation between the lever arm and the catalytic domain were tested by measuring separation distances among myosin subfragment-2, the nucleotide site, and the regulatory light chain in the presence of nucleotide...
متن کاملDifferent degrees of lever arm rotation control myosin step size
Myosins are actin-based motors that are generally believed to move by amplifying small structural changes in the core motor domain via a lever arm rotation of the light chain binding domain. However, the lack of a quantitative agreement between observed step sizes and the length of the proposed lever arms from different myosins challenges this view. We analyzed the step size of rat myosin 1d (M...
متن کاملCalcium gets myosin VI ready for work.
The myosins are a large family of actin-binding motor proteins that convert stored chemical energy into work, with important functions in intracellular transport, force generation, and mechanosensation (1). Despite many advances in understanding the mechanical and kinetic properties of purified myosins in vitro, the signals that regulate the functions of these molecular motors in cells are not ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Biochemistry
دوره 40 26 شماره
صفحات -
تاریخ انتشار 2001