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Structural basis for the slow dynamics of the actin filament pointed end
Author(s) -
Narita Akihiro,
Oda Toshiro,
Maéda Yuichiro
Publication year - 2011
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/emboj.2011.48
Subject(s) - protein filament , actin , biophysics , protein subunit , treadmilling , biology , polarity (international relations) , depolymerization , microfilament , monomer , cytoskeleton , microbiology and biotechnology , polymer , physics , biochemistry , materials science , cell , nuclear magnetic resonance , polymer chemistry , gene
The actin filament has clear polarity where one end, the pointed end, has a much slower polymerization and depolymerization rate than the other end, the barbed end. This intrinsic difference of the ends significantly affects all actin dynamics in the cell, which has central roles in a wide spectrum of cellular functions. The detailed mechanism underlying this difference has remained elusive, because high‐resolution structures of the filament ends have not been available. Here, we present the structure of the actin filament pointed end obtained using a single particle analysis of cryo‐electron micrographs. We determined that the terminal pointed end subunit is tilted towards the penultimate subunit, allowing specific and extra loop‐to‐loop inter‐strand contacts between the two end subunits, which is not possible in other parts of the filament. These specific contacts prevent the end subunit from dissociating. For elongation, the loop‐to‐loop contacts also inhibit the incorporation of another actin monomer at the pointed end. These observations are likely to account for the less dynamic pointed end.