Myosin family analysis

The myosins constitute one of the largest and most divergent protein families in eukaryotes [1]. They are characterized by a motor domain that binds to actin in an ATP-dependent manner, a neck domain consisting of varying numbers of IQ motifs, and amino-terminal and carboxy-terminal domains of various length and function [2]. Myosins are involved in many cellular tasks like organelle trafficking, cytokinesis, maintenance of cell shape, muscle contraction, and others. Myosins are typically classified based on phylogenetic analyses of the motor domain [3].

We are continously annotating all myosins from newly finished eukaryotic genomes or from EST sequencing projects. In September 2007 our analysis based on the data available in Februar 2007 has been published [4]. Based on the phylogenetic tree constructed from 1984 myosin motor domains, 35 classes have been assigned (Figure 1-3). 149 myosins still remain unclassified due to our conservative view on designating classes but it is anticipated that sequencing of further genomes will result in their classification and will substantially increase the existing number of classes. So far, almost all orphan myosins belong to taxa that have not undergone large-scale comparative sequencing efforts. The highest number of myosins in a single organism has been found in Brachydanio rerio (61 myosins grouped into 13 classes) while the broadest class distribution is expected for the Phytophthora species (25 myosins grouped into at least 15 classes).

Myosin statistics Myosin tree Myosin domain organisation
Figure 1

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Figure 2

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Figure 3

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[1]M Krendel M, MS Mooseker: Myosins: tails (and heads) of functional diversity. Physiology (Bethesda) 2005, 20:239-51.
[2]M Schliwa, G Woehlke: Molecular motors. Nature 2003, 422:759-65.
[3]RE Cheney, MA Riley, MS Mooseker: Phylogenetic analysis of the myosin superfamily. Cell Motil Cytoskeleton 1993, 24:215-223.
[4]F Odronitz, M Kollmar: Drawing the tree of eukaryotic life based on the analysis of 2269 manually annotated myosins from 328 species. Genome Biology 2007, 8:R196.
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