Structure and orientation of troponin in the thin filament

D M Paul, E P Morris, R W Kensler, JM Squire

Research output: Contribution to journalArticle (Academic Journal)peer-review

23 Citations (Scopus)


The troponin complex on the thin filament plays a crucial role in the regulation of muscle contraction. However, the precise location of troponin relative to actin and tropomyosin remains uncertain. We have developed a method of reconstructing thin filaments using single particle analysis that does not impose the helical symmetry of actin and is independent of a starting model. We present a single particle three-dimensional reconstruction of the thin filament. Atomic models of the F-actin filament were fitted into the electron density maps and troponin and tropomyosin located. The structure provides evidence that the globular head region of troponin labels the two strands of actin with a 27.5-A axial stagger. The density attributed to troponin appears tapered with the widest point toward the barbed end. This leads us to interpret the polarity of the troponin complex in the thin filament as reversed with respect to the widely accepted model.
Translated title of the contributionStructure and orientation of troponin in the thin filament
Original languageEnglish
Pages (from-to)15007 - 15015
Number of pages9
JournalJournal of Biological Chemistry
Publication statusPublished - May 2009

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