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-Structure paper
Title | Structure of the acrosomal bundle. |
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Journal, issue, pages | Nature, Vol. 431, Issue 7004, Page 104-107, Year 2004 |
Publish date | Sep 2, 2004 |
![]() | Michael F Schmid / Michael B Sherman / Paul Matsudaira / Wah Chiu / ![]() |
PubMed Abstract | In the unactivated Limulus sperm, a 60- micro m-long bundle of actin filaments crosslinked by the protein scruin is bent and twisted into a coil around the base of the nucleus. At fertilization, the ...In the unactivated Limulus sperm, a 60- micro m-long bundle of actin filaments crosslinked by the protein scruin is bent and twisted into a coil around the base of the nucleus. At fertilization, the bundle uncoils and fully extends in five seconds to support a finger of membrane known as the acrosomal process. This biological spring is powered by stored elastic energy and does not require the action of motor proteins or actin polymerization. In a 9.5-A electron cryomicroscopic structure of the extended bundle, we show that twist, tilt and rotation of actin-scruin subunits deviate widely from a 'standard' F-actin filament. This variability in structural organization allows filaments to pack into a highly ordered and rigid bundle in the extended state and suggests a mechanism for storing and releasing energy between coiled and extended states without disassembly. |
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Methods | EM (helical sym.) |
Resolution | 9.5 Å |
Structure data | ![]() EMDB-1088: |
Source |
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