Sensitivity of Eleusine indica Callus to Trifluralin and Amiprophosmethyl in Correlation with the Binding of These Compounds to Tubulin

The sensitivity of calluses derived from susceptible and resistant goosegrass (Eleusine indica (L.) Gaertn.) biotypes to dinitroaniline herbicides, which disrupt interphase and mitotic-spindle microtubules, was evaluated. A callus culture derived from the resistant biotype retained resistance to both trifluralin (dinitroaniline herbicide) and amiprophosmethyl (phosphorothioamidate herbicide). The site for the interaction between -tubulin subunit and dinitroaniline or phosphorothioamidate herbicides was identified by computer simulation. A correlation was found between the level of callus sensitivity to herbicide tested and the pattern of herbicide interaction with -tubulin.     

Structural and biological characterization of the tubulin interaction with dinitroanilines

Characteristics of the interaction of dinitroaniline compounds with tubulin molecules have an extremely high selectivity: these substances efficiently bind to the tubulins of both plant and protozoan origins and practically do not interact with any animal and fungal tubulins despite a very high similarity between the corresponding sequences. This work summarizes and comprehensively analyzes the specific structural features and mechanisms of these interactions, in particular, the patterns of the structure and arrangement of dinitroaniline binding sites on the surface of different tubulin subunits and tubulins of various origins. Dinitroaniline binding sites are localized to the surface of longitudinal contacts between tubulin subunits and contain diamine amino acid residues (lysine or arginine), which bind the nitrile group of dinitroanilines. The localizations of these sites on the surface of identical subunits of different origins (for example, α-tubulins of plants and protozoans) coincide; however, the location of these binding sites on the surfaces of tubulin α- and β-subunits is different. The characterized sites can also be potential binding sites for other antimicrotubule compounds, in particular, cyanoacrylates.     

Bioinformatic search of plant protein kinases involved in the phosphorylation of microtubular proteins and the regulation of the cell cycle

The bioinformatic search of the plant homologues of human protein kinases SLK, PAK6, PAK7, MARK1, MAST2, TTBK1, TTBK2, AURKA, PLK1, PLK2, and PASK, involved in the phosphorylation of microtubular proteins and regulation of cell division, was carried out. The plant homologues of protein kinases SLK, MAST2, and AURKA were identified. It was found that the closest homologue of human protein kinase AURKA is a protein A7PY12_VITVI (STALK, Serine-Threonine Aurora-Like Kinase) from grapes (Vitis vinifera), whose function is still unknown. The reconstruction and analysis of the 3D-structure of the STALK protein confirmed its relation to the group of AURKA-like protein kinases.     

Structural mechanisms of interaction of cyanolcrylates with plant tubulin

The structural mechanisms underlying the specific binding of cyanoacrylate compounds with tubulin of higher plants have been studied by the example of the interaction of ethyl-(2Z)-3-amino-2-cyano-4-ethylhex-2-enoate (CA1) and isopropyl-(2Z)-3-amino-2-cyano-4-ethylhex-2-enoate (CA2) with Arabidopsis thaliana α-tubulin. It was revealed that the cyano group of cyanoacrylates is a functional analogue of the nitrile group, which determines the processes of specific interaction with plant tubulin for dinitroaniline compounds. Based on data on spatial structure fluctuations, the dynamics of hydrogen bonds and the interaction energy of CA1 and CA2 (the most probable binding mode for these compounds with plant α-tubulin) was identified and the appropriate site of interaction was characterized. Seven out of ten residues composing this site (Gln-133, Asn-249, Val-250, Asp-251, Val-252, Asn-253, and Glu-254) are obligatory components of dinitroanilines’ binding site on the plant α-tubulin surface. Thus, the binding site on the α-tubulin surface characterized by us is able to recognize and specifically bind substances, which are cardinally different by their chemical nature and have no common pharmacophore groups, under the condition of a certain similarity of their electrostatic topology.     

Molecular and structural-biological analysis of <Emphasis Type="Italic">Nicotiana plumbaginifolia</Emphasis> mutants for identification of the site on their β-tubulins of interaction with dinitroanilines and phosphorothioamides

The identification of the location of a point mutation on β-tubulin molecules of amiprophosmethyland trifluralin-resistant Nicotiana plumbaginifolia lines are described in this work. It was shown that in the first case, this mutation is related with the substitution of serine residue for proline in position 248; in the second case, with the substitution of phenylalanine for serine in position 317 of the β-tubulin’s amino acid sequence. Three-dimensional models of the β-tubulin molecule from Chlamydomonas with the well-known location of mutations determining dinitroaniline- and phosphorothioamides resistance (the substitution of lysine residue for methionine in position 350), and β-tubulin from Nicotiana plumbagnifolia have been reconstructed. On the basis of the analysis of the interaction site for dinitroanilines and phosphorothioamides located on the Chlamydomonas β-tubulin’s molecule it was concluded that the revealed mutations on Nicotiana plumbaginifolia β-tubulin are affected by the residues of the amino acids, participating in the formation of this site.