Evolutionary traces decode molecular mechanism behind fast pace of myosin XI

To provide sequence determinants and structural rationale for the molecular mechanism of this fast pace myosin, we have compared the sequences from myosin class V and XI through Evolutionary Trace (ET) analysis. The current study identifies class-specific residues of myosin XI spread over the actin binding site, ATP binding site and light chain binding neck region. Sequences for ET analysis were accumulated from six plant genomes, using literature based text search and sequence searches, followed by triple validation viz. CDD search, string-based searches and phylogenetic clustering. We have identified nine myosin XI genes in sorghum and seven in grape by sequence searches. Both the plants possess one gene product each belonging to myosin type VIII as well. During this process, we have re-defined the gene boundaries for three sorghum myosin XI genes using fgenesh program.Molecular modelling and subsequent analysis of putative interactions involving these class-specific residues suggest a structural basis for the molecular mechanism behind high velocity of plant myosin XI. We propose a model of a more flexible switch I region that contributes to faster ADP release leading to high velocity movement of the algal myosin XI.Myosin is an actin based motor protein that generates motion using chemical energy released through ATP hydrolysis. Myosins play many important roles within plant cells such as organelle trafficking [1,2], remodelling [3,4], and inheritance [5]. They are also known to be involved in development of various plant parts like root hairs, pollen etc [6,7]. Though there are around 24 classes of myosins reported in eukaryota [8], only three classes - class VIII, XI and XIII are seen in plants. The similarity of plant myosin sequences with animal and fungal class V myosins [9], derived from phylogenetic analysis, suggests a common ancestor from which plants and Opisthokonts [10] might have evolved.Myosins, in general, function through an ATP hydrolysis cycle