Analysis of structural characteristics of alpha-tubulins in plants with enhanced cold tolerance

The uniqueness of the point substitutions in the sequences of two alpha-tubulin isotypes from psychrophilic alga Chloromonas that can determine the increased cold tolerance of this alga was analyzed. The comparison of all known amino acid sequences of plant alpha-tubulins enabled to ascertain that only M268-->V replacement is unique and may have a significant influence on spatial structure of plant alpha-tubulins. Modeling of molecular surfaces of alpha-tubulins from Chloromonas, Chalmydomonas reinhardtii and goose grass Eleusine indica showed that insertion of the amino acid replacement M268-->V into the sequence of goose grace tubulin led to the likening of this protein surface to the surface of native alpha-tubulin from Chloromonas. Alteration of local hydrophobic properties of alpha-tubulin molecular surface in interdimeric contact zone as a result of the mentioned replacement was shown that may play important role in increasing the level of cold resistance of microtubules. The crucial role of amino acid residue in 268 position for forming the interdimeric contact surface of alpha-tubulin molecule was revealed. The assumption is made about the importance of replacements at this position for plant tolerance to abiotic factors of different nature (cold, herbicides).     

Construction of three-dimensional models of Arabidopsis thaliana FtsZ-proteins on basis of crystal structure of archaebacterial FtsZ-GDP complex

Three-dimensional models of FtsZ-protein complexes with GDP from Arabidopsis thaliana L. localized in cytosol (Entrez database code NP190843) and in chloroplasts (Entrez database code AAA82068) were developed. Crystal structure of the FtsZ-GDP complex from archaea Methanococcus jannaschii (PDB-code 1FSZ) was used as a matrix. Secondary structures of computed models contain ten beta-strands. A chloroplast form of FtsZ-protein has ten alpha-helices and four 3(10)-helices, whereas cytosolic form of protein has nine and three structures correspondently and neither a0-helix before nucleotide-binding domain nor C-terminal 3(10)-helix in secondary domain. The T2-loop of nucleotide-binding pocket of chloroplast form of FtsZ-ptotein in position 111 contains non-charged alanin residue instead of the charged one which is typical for cytosolic and bacterial forms of proteins. At low sequence homology of FtsZ-proteins (approximately 47%) the developed models demonstrate high coincidence with matrix both in the structures of nucleotide-binding pocket and in the whole molecule. The models are completely suitable for further studies of possible sites of binding with dinitroaniline herbicides.     

Exposure of beta-tubulin regions defined by antibodies on an <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>microtubule protofilament model and in the cells

Background  

The function of the cortical microtubules, composed of αβ-tubulin heterodimers, is linked to their organizational state which is subject to spatial and temporal modulation by environmental cues. The role of tubulin posttranslational modifications in these processes is largely unknown. Although antibodies against small tubulin regions represent useful tool for studying molecular configuration of microtubules, data on the exposure of tubulin epitopes on plant microtubules are still limited.     

Reconstruction of spatial structure of plant protein phosphatase type-1 and -2A in complex with okadaic acid

The homology modeling, based on known temple structures of Homo sapiens protein phosphatase type-1 and -2A was implemented. The spatial structures of the human protein phosphatases and their plant homologs from Arabidopsis thaliana was predicted. The quality of models was confirmed by conformational analysis and root mean square deviations. The sites of okadaic acid binding in molecules of plant protein phosphatases (type-1 and -2A) were proved by the data of comparative analysis and molecular dynamics.     

Bioinformatics search for plant homologues of Ste20-like serine/threonine protein kinases

Eleven plant homologuess of animal and yeast STE20-like protein kinases were identified. It was shown that unknown proteins A9RVK0 of the moss Physcomitrella patens ssp. patens and A7P2E2 of the grape Vitis vinifera were the closest plant homologues of STE20-like protein kinases. The Ste20-like protein kinase dst1 of the myxomycete Dictyostelium discoideum was the closest to the plant homologues. The spatial structure of the catalytic domain of the protein A9RVK0 from P. patens ssp. patens was predicted.     

Comparative analysis of primary structure of the mutant tubulins with resistance to antimicrotubular drugs for prediction of new mutations with analogous properties

All known for today complete amino acid sequences of alpha- and beta-tubulins were aligned and analyzed to reveal the regularity of location of mutations result in the resistance to antimicrotubular compounds and a prediction of positions of new similar mutations. It was shown, that known positions of amino acid changes lead to decrease a affinity to antimicrotubular agents with depolymerizing mechanism of action are consensus and located in proximity to the residues involved in intradimeric/interdimeric interactions and interactions with nucleotides (within of six residues), but never coincide with them. For changes lead to resistance to stabilizing antimicrotubular compounds, similar dependence is not traced. The identified regularity enables to predict the positions of new mutations lead to resistance to agents with depolymerizing mechanism of action.