Molecular modeling of the myosin-S1(A1) isoform.

Type II myosin is the molecular motor which drives contraction upon cyclic interaction with filamentous actin while consuming ATP. The contemporary crystallographic structure of the myosin subfragment-1 (S1) of myosin covers both the motor domain of the heavy chain (MHC) as well as the essential (ELC) and regulatory light chains (RLC). A part of the N-terminus of the ELC is, however, missing in the 3D-models of Type II myosin. The N-terminal domain of the ELC comprises interesting functional features since it binds to actin thus controlling myosin motor activity. For the first time, we modeled the missing 46 N-terminal amino acid of the ELC to the contemporary actin-myosin-S1 complex. We show a rod-like 91 A structure being long enough to bridge the gap between the ELC core of myosin-S1 and the appropriate binding site of the ELC on the actin filament.