Domain Complexity of Plant Kinesins

The Arabidopsis Genome Contains 61 Kinesins, The Largest Kinesin Family Of Any Fully Sequenced And Annotated Genome. Characterizing Each Member Of A Large Protein Family Is A Difficult And Laborious Task, Not Only Due To The Size, But Also The Inherent Diversification And/Or Redundancy Associated With Gene Duplication. An Alternative Approach To Better Understand The Arabidopsis Kinesin Family Is To Study The Domain Composition Of These Proteins. Domains Are Defined As The Structural And Functional Units Of Proteins. Understanding The Domains And Domain Structure Of An Unknown Protein Often Allows For A Reliable Prediction Of Function When Experimental Evidence Is Unavailable. Kinesins Share A Highly Conserved Motor Domain With Low Sequence Similarity Outside Of This Domain, And Many Members Contain Additional Protein Domains In The Nonconserved Regions. New Arrangements Of Domains, By Means Of Genetic Duplication, Replication, Or Loss, Result In Novel Proteins With Unique Functions. Using Both The Arabidopsis And Other Sequenced Genomes, It Was Found That Several Kinesins Have Protein Domain Arrangements Specific To Different Lineages, Providing Compelling Evidence For The Evolution Of Kinesins With Novel Functions. A Phylogenic Analysis Of Plant-Specific Kinesin Domains, As Well As A Comparative Review Of The Molecular/ Biochemical Functions Of These Domains, Is Presented In This Chapter. Combined, They Provide An Alternative Means To Understanding And Developing More Direct And Relevant Hypotheses Concerning Novel Kinesins.