THE COMPARISON OF COLCHICINE, VINBLASTINE AND TAXOL BINDING SITES
ON ANIMAL AND PLANT TUBULINS
Pydiura N.A., Karpov P.A., Blume Y.B.
Institute of Food Biotechnology and Genomics NAS of Ukraine, 04123 Кyiv, Оsipovskogo,
2A, Ukraine
Derivatives of plant alkaloids such as colchicine, vinblastine and taxol bind to tubulins and
have a wide application in medicine and biotechnology affecting microtubules
(de)polymerization. It's well known that distinctness through variations in key amino acid
residues of binding sites determine sensitivity or resistance to the same drug. The colchicine,
vinblastine and taxol sites in animal tubulins are known from Portein Data Bank structures:
3DU7, 3Z2B (Bos taurus) and 1TUB (Sus scrofa) respectively. Colchicine binds to tubulin at
a single site formed by Ser178 of α-tubulin and Leu255, Ala316 of β-tubulin. Vinblastine site
is formed by Pro325, Asn329, Val353 and Ile355 of α-tubulin and Val177, Tyr210, Tyr224 of
β-tubulin. Taxol site is formed by Val23, His229, Phe272, Thr276 and Pro360 of β-tubulin.
We compare the amino acid sequences of animal tubulins (for which colchicine, vinblastine
and taxol sites are known) with tubulins from dicot (Arabidopsis, Glycine, Medicago) and
monocot (Oryza, Triticum, Zea) flowering plants.
Plants usually contain more (up to 10) tubulin genes than animal genomes. But genome
sequencing coverage for selected plant species is different. For both Arabidopsis and Oryza
we analyzed 3 α- and 8 β-tubulin reviewed sequences from UniProtKB/Swiss-Prot. For Zea,
Triticum and Glycine 6 α- / 8 β-, 1 α- / 5 β- and 3 β-tubulin reviewed sequences were analyzed
respectively. For Medicago 5 α- and 10 β-tubulin unreviewed (UniProtKB/TrEMBL)
sequences were analyzed. Multiple sequence alignments of the named sequences were
performed using ClustalW.
It was revealed that in plant colchicine-binding site, α-tubulin Val353 is replaced by Cys and
β-tubulin Ala316 is replaced by Ser. Other a.a. residues of colchicine site are conserved. In
plant vinblastine-binding site we identified substitutions: Val353Cys in α-tubulin and
Ala316Ser in β-tubulin. The rest of the residues are identical to corresponding residues of
animal tubulins. In taxol site Thr276 of plant α-tubulin was substituted by Ala only in isoform
beta 2 of Glycine but in other sequences it is conserved. Also in 2 of 10 unreviewed β-tubulins
from Medicago (UniProt IDs Q949G6 and G7LDD) Val23 of taxol-binding site corresponds
to a single nucleotide deletion and a substitution to Ala respectively.
Our results demonstrate that colchicine-, vinblastine- and taxol-binding sites are almost
completely conserved in all plant α-/β-tubulins. The Val353Cys (in α-tubulin) and Ala316Ser
(β-tubulin) substitutions in plants colchicine binding site may lead to critical differences in the
nature of this binding site in plants compared to animals. At the same time, in plants
vinblastine-binding site substitution of Tyr224 in β-tubulin by similar aromatic a.a. Phe may
be much less significant. In turn, amino acid positions that are involved in taxol-binding in
plant and animal tubulins proved to be extremely conservative.