期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2004
卷号：101
期号：33
页码：12189-12194
DOI：10.1073/pnas.0404835101
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Acanthamoeba myosin IC (AMIC) is a single-headed myosin comprised of one heavy chain (129 kDa) and one light chain (17 kDa). The heavy chain has head, neck (light chain-binding), and tail domains. The tail consists of four subdomains: a basic region (BR) (23 kDa) and two Gly/Pro/Ala-rich (GPA) regions, GPA1 (6 kDa) and GPA2 (15 kDa), flanking an Src homology 3 region (6 kDa). Although the AMIC head is similar in sequence, structure, and function (ATPase motor) to other myosin heads, the organization of the tail has been less clear as has its function beyond an assumed role in binding interaction partners, e.g., the BR has a membrane affinity and the GPA components bind F-actin in an ATP-independent manner. To investigate the spatial arrangement of subdomains in the tail, we have used cryo-electron microscopy and image reconstruction to compare actin filaments decorated with WT AMIC and tail-truncated mutants of various lengths. The BR forms an oval-shaped feature, {approx}40 A long, that diverges obliquely from the head, extending azimuthally around the actin filament and toward its barbed end. GPA2 and GPA1 are located together on the inner (actin-proximal) side of the tail, close enough to act in concert in binding the same or another actin filament. The outer face of the BR is strategically exposed for membrane or vesicle binding.
