Microtubule is an important structural and functional component in cells.Microtubule-associated proteins(MAPs)are a class of proteins that can bind to microtubules and stabilize them to maintain their functions.However,not all the specific microtubule-binding domains on MAPs are clear.Here we report the study of microtubule-binding domains on MAPs from a new angle by biopanning a new type of phage-displayed random peptide library(called landscape phage library)against purified alpha-and beta-tubulins.In the landscape phage library,billions of fd-tet phage clones are present and a unique 9-mer peptide is fused to each of the ~3900 copies of major coat protein(pVIII)in each clone.The affinity-selected peptides derived from the biopanning were analyzed by the receptor ligand contacts(RELIC)suite of programs,which is a bioinformatics tool for combinatorial peptide analysis and identification of protein-ligand interaction sites.By using RELIC,the affinity-selected peptides were shown to have similarity with the sequences of two MAP families(MAP1 and MAP2/tau),thereby identifying putative microtubule-binding domains on these MAPs.The tubuUn-binding affinity was also confirmed by using transmission electron microscopy(TEM)to characterize the interaction between affinity-selected tubulin-binding phage and tubulins.Our results confirm some known microtubule-binding domains and identify some new microtubule-binding domains and thus shed light into the mechanism of microtubule-MAPs interactions.
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