Regulation of calmodulin-binding myosins

Interaction of Arabidopsis kinesin‐like calmodulin‐binding protein with tubulin subunits: modulation by Ca2+‐calmodulin

“…Among motor proteins light chains of bovine brain kinesin and actin-based unconventional myosin heavy chains are the only ones that bind to calmodulin (Matthies et al, 1993;Wolenski, 1995). The binding of calmodulin to kinesin light chain inhibits kinesin's microtubule stimulated ATPase activity by 50% (Matthies et aL, 1993).…”

“…Phosphorylation of kinesin by protein kinase A reverses the calmodulin inhibition of ATPase activity. Many unconventional myosins bind calmodulin in the absence of calcium which is contrary to most target enzymes including KCBP that bind calmodulin in the presence of calcium (Wolenski, 1995). In the case of brush border myosin I, calcium causes partial dissociation of calmodulin from the motor resulting in complete inhibition of motility (Wolenski et al, 1993).…”

Intermolecular tuning of calmodulin by target peptides and proteins: Differential effects on Ca2+ binding and implications for kinase activation

“…The ubiquitous protein calmodulin (CaM) plays a crucial role in Ca2+ signaling (Beckingham, 1995;Braun & Schulman, 1995; Clapham, 1995;Wolenski, 1995; Berridge, 1996), where it regulates a wide range of cellular processes by serving as an intracellular receptor for Ca2+ ions (Wheeler et al…”

“…Overall, the results indicate that the cellular activation of myosin light chain kinase is likely to be triggered by the binding of free CaZ2+-CaM or Cq2+-CaM after a Ca2+ signal has begun and that inactivation of the complex is initiated by a single rate-limiting event, which is proposed to be either the direct dissociation of Ca2+ ions from the bound C-terminal domain or the dissociation of Ca2+ loaded C-terminal domain from skMLCK. The observed target-induced variations in Ca2+ affinities and dissociation rates could serve to tune CaM activation and inactivation for different cellular pathways, and also must counterbalance the variable energetic costs of driving the activating conformational change in different target enzymes.Keywords: calcium signaling; calmodulin; kinase regulation; protein-protein interactionsThe ubiquitous protein calmodulin (CaM) plays a crucial role in Ca2+ signaling (Beckingham, 1995;Braun & Schulman, 1995; Clapham, 1995;Wolenski, 1995; Berridge, 1996), where it regulates a wide range of cellular processes by serving as an intracellular receptor for Ca2+ ions (Wheeler et al …”

Nucleomorphin

“…Many Ca 2ϩ -independent CaMBPs exist, adding to the complexity of CaM regulation and function. CaM also interacts in a Ca 2ϩ -independent manner through an IQ motif, as has been shown for conventional type II myosin light chains and the unconventional myosins, neuromodulin and neurogranin (17)(18)(19). Because CaM's target proteins (CaMBPs) do the work, a full understanding of their structure, function, and regulation is essential, but, as yet, the full complement of CaMBPs has not been determined for any cell type.…”