Figure 1. An unrooted phylogenetic tree of the myosin superfamily. The tree is derived from an alignment of 145 members of the myosin superfamily. This alignment compares the core motor domains (equivalent to amino acids 88–780 of chicken skeletal myosin II) of each myosin using distance matrix analysis performed with the Clustal-W package. The exceptions, shown with a dotted line, are SsVIIa, a partial sequence in the databases and Hs MysPDZ, which has a truncated amino end starting some 52 residues into the core motor region. Gap positions in the alignment were included during bootstrap analysis (repeated redrawing of the tree structure to yield confidence estimates) in order not to exclude a large proportion of the data. Being unrooted, the relationships between classes as shown by the branching order at the centre of the tree are unreliable but evolutionary information can be derived within a class. The molecular cartoons serve to indicate possible molecular structure, especially the expected single or double headed nature of the myosins.

Figure 2. Myosin domain structure as predicted from sequence analysis. The predicted functional domains identified in the various myosin classes are shown graphically for representatives of each class. The protein sequence bars and domain sizes are only approximately to scale; hence no scale is given. Note the motor domains are relatively conserved whereas the tail domains are highly variable. Those regions in the tails in white (blank) are those so far without any recognizable homologies.