Crystal structure of the motor domain of a class-I myosin

The crystal structure of the motor domain of Dictyostelium discoideum myosin-IE, a monomeric unconventional myosin, was determined. The crystallographic asymmetric unit contains four independently resolved molecules, highlighting regions that undergo large conformational changes. Differences are particularly pronounced in the actin binding region and the converter domain. The changes in position of the converter domain reflect movements both parallel to and perpendicular to the actin axis. The orientation of the converter domain is ∼30° further up than in other myosin structures, indicating that MyoE can produce a larger power stroke by rotating its lever arm through a larger angle. The role of extended loops near the actin-binding site is discussed in the context of cellular localization. The core regions of the motor domain are similar, and the structure reveals how that core is stabilized in the absence of an N-terminal SH3-like domain.

本研究解析了单体非常规肌球蛋白盘基网柄菌（Dictyostelium discoideum）肌球蛋白IE（MyoE）的马达结构域晶体结构。该晶体学不对称单元中包含4个独立解析的分子，凸显了发生大规模构象变化的区域。肌动蛋白结合区域与转换器结构域的差异尤为显著。转换器结构域的位置变化反映了平行于和垂直于肌动蛋白轴的双向运动。相较于其他肌球蛋白结构，该转换器结构域的取向高出约30°，表明MyoE可通过其杠杆臂的更大角度旋转，产生更大的动力冲程。本文结合细胞定位的相关情境，讨论了肌动蛋白结合位点附近延伸环的功能作用。该马达结构域的核心区域结构保守，本结构还阐明了在缺失N端类SH3结构域时，核心区域的稳定方式。