Kinetic mechanism ofNicotiana tabacummyosin‐11 defines a new type of a processive motor

Abstract

The 175-kDa myosin-11 from Nicotiana tabacum (Nt 175kDa myosin-11) is exceptional in its mechanical activity as it is the fastest known processive actin-based motor, moving 10 times faster than the structurally related class 5 myosins. Although this ability might be essential for long-range organelle transport within larger plant cells, the kinetic features underlying the fast processive movement of Nt 175kDa myosin-11 still remain unexplored. To address this, we generated a single-headed motor domain construct and carried out a detailed kinetic analysis. The data demonstrate that Nt 175kDa myosin-11 is a highduty ratio motor, which remains associated with actin most of its enzymatic cycle. However, different from other processive myosins that establish a high duty ratio on the basis of a rate-limiting ADP-release step, Nt 175kDa myosin-11 achieves a high duty ratio by a prolonged duration of the ATP-induced isomerization of the actin-bound states and ADP release kinetics, both of which in terms of the corresponding time constants approach the total ATPase cycle time. Molecular modeling predicts that variations in the charge distribution of the actin binding interface might contribute to the thermodynamic fine-tuning of the kinetics of this myosin. Our study unravels a new type of a high duty ratio motor and provides important insights into the molecular mechanism of processive movement of higher plant myosins.-Diensthuber, R. P., Tominaga, M., Preller, M., Hartmann, F. K., Orii, H., Chizhov, I., Oiwa, K., Tsiavaliaris, G. Kinetic mechanism of Nicotiana tabacum myosin-11 defines a new type of a processive motor. FASEB J. 29, 81-94 (2015). www.fasebj.org

Update on Myosin Motors: Molecular Mechanisms and Physiological Functions

“…These results were confirmed by direct experimental modification of a Dictyostelium discoideum myosin (Ito et al, 2009) and also are consistent with a comparison of structural homology models of different myosin motors (Diensthuber et al, 2015). It has been proposed that subtle differences in charge distributions in these two loops, as well as other places within the actin-binding region of myosin XI, also can explain the increased processivity of tobacco myosin XI (Diensthuber et al, 2015), but experimental evidence for this prediction is still missing. Better characterization of the structure-function relationship of myosin motor activities across the spectrum of motor activity will allow us not only to predict the motor properties of uncharacterized myosins but also to manipulate the functions of individual isoforms in a targeted way.…”

“…Targeted mutagenesis of C. corallina motors has revealed that the charge distribution between two surface loops within the actinbinding domain of the motor influences the turnover rate by modulating the rate of ADP release (Ito et al, 2009). These results were confirmed by direct experimental modification of a Dictyostelium discoideum myosin (Ito et al, 2009) and also are consistent with a comparison of structural homology models of different myosin motors (Diensthuber et al, 2015). It has been proposed that subtle differences in charge distributions in these two loops, as well as other places within the actin-binding region of myosin XI, also can explain the increased processivity of tobacco myosin XI (Diensthuber et al, 2015), but experimental evidence for this prediction is still missing.…”

“…As a result, the duty ratio of the motor is only 0.3 and dimers of myosin XI in C. corallina are not processive . Interestingly, a 175-kD myosin XI in tobacco is still processive despite rapid ADP release by slowing down the motor isomerization after initial binding of ATP, which maintains the motor in its tightly bound state longer (Diensthuber et al, 2015).…”

Increased miltefosine tolerance in clinical isolates of Leishmania donovani is associated with reduced drug accumulation, increased infectivity and resistance to oxidative stress

“…donovani parasites adopt metabolic reconfiguration by shift in primary carbon metabolism to subvert oxidative stress posed by antileishmanial drug [34]. The key enzymes of glycolytic pathway [12] and glucose uptake remain unaltered during stress in Leishmania [34].…”

Navigating the plant cell: intracellular transport logistics in the green kingdom

“…These remarkable speeds seem to be possible because of subtle changes in the otherwise highly conserved myosin motor ( Ito et al. , 2009 ; Henn and Sadot, 2014 ; Diensthuber et al. , 2015 ).…”