Rationalization of paclitaxel insensitivity of yeast β-tubulin and human βIII-tubulin isotype using principal component analysis

Lalita Das,Gautam Basu,Bhabatarak Bhattacharya

doi:10.1186/1756-0500-5-395

Abstract

BackgroundThe chemotherapeutic agent paclitaxel arrests cell division by binding to the hetero-dimeric protein tubulin. Subtle differences in tubulin sequences, across eukaryotes and among β-tubulin isotypes, can have profound impact on paclitaxel-tubulin binding. To capture the experimentally observed paclitaxel-resistance of human βIII tubulin isotype and yeast β-tubulin, within a common theoretical framework, we have performed structural principal component analyses of β-tubulin sequences across eukaryotes.ResultsThe paclitaxel-resistance of human βIII tubulin isotype and yeast β-tubulin uniquely mapped on to the lowest two principal components, defining the paclitaxel-binding site residues of β-tubulin. The molecular mechanisms behind paclitaxel-resistance, mediated through key residues, were identified from structural consequences of characteristic mutations that confer paclitaxel-resistance. Specifically, Ala277 in βIII isotype was shown to be crucial for paclitaxel-resistance.ConclusionsThe present analysis captures the origin of two apparently unrelated events, paclitaxel-insensitivity of yeast tubulin and human βIII tubulin isotype, through two common collective sequence vectors.

Highlights

The chemotherapeutic agent paclitaxel arrests cell division by binding to the hetero-dimeric protein tubulin
When five amino acid residues in yeast β-tubulin (A19K, T23V, G26D, N229H, and Y272F) were changed to the respective residues found in the mammalian brain tubulin, a paclitaxel-binding site could be created in yeast tubulin [20]
From a multiple sequence alignment using the program ClustalW [24], amino acids corresponding to the 22 paclitaxel binding site (PBS) residues were identified in 125 eukaryotic β-tubulin sequences, as shown in Figure 1

Summary

Introduction

The chemotherapeutic agent paclitaxel arrests cell division by binding to the hetero-dimeric protein tubulin. Paclitaxel, a product of plant secondary metabolism, binds to the β-tubulin subunit and inhibits microtubule dynamics, thereby blocking cell cycle progression during mitosis at the metaphase/anaphase transition and activating cell death [6,7,8]. It is an important cancer chemotherapeutic agent for treatment of advanced ovarian, Similar to the βIII isotype of mammalian brain tubulin, tubulin from the budding yeast, Saccharomyces cerevisiae, shows weak binding affinity for paclitaxel [18,19] despite the fact that yeast tubulin shares 75% amino acid identity with mammalian brain tubulin. This is analogous to the difference between βIII tubulin and other β-tubulin isotypes (they differ at only a few sequence positions) where a dramatic change in paclitaxel affinity is observed

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Discussion

Conclusion