The role of caldesmon and its phosphorylation by ERK on the binding force of unphosphorylated myosin to actin

摘要: Smooth muscle has the unique property of maintaining tension with low ATP consumption. It is generally accepted that this property, called latch-state, results from dephosphorylation myosin while attached to actin. However, detached dephosphorylated can also bind actin and contribute force maintenance. We investigated effect caldesmon on binding unphosphorylated quantified average unbinding (Funb) in absence or presence caldesmon, ERK phosphorylated plus tropomyosin. Briefly, a microsphere captured single beam laser trap was fluorescently labeled filament then brought contact pedestal coated myosin. The moved away at constant velocity. actin/microsphere followed until exerted by exceeded At point, sprang back into center. Funb calculated as product stiffness maximal displacement normalized number molecules estimated per length. unregulated (0.09±0.01 pN) significantly increased (0.17±0.02 pN), tropomyosin both regulatory proteins (0.18±0.02 pN). Interestingly, phosphorylation reduced (0.06±0.01 Thus, enhances potentially contributing latch-state. Conversely, decreases very levels, suggesting mechanism for relaxation latch-state.Supported by: NSERC, NIH-RO1HL103405