End-to-end annealing of plant microtubules by the p86 subunit of eukaryotic initiation factor-(iso)4F.

The p86 subunit of eukaryotic initiation factor-(iso)4F from wheat germ exhibits saturable and substoichiometric binding to maize microtubules, induces microtubule bundling in vitro, and is colocalized or closely associated with cortical microtubule bundles in maize root cells, indicating its function as a microtubule-associated protein (MAP). The effects of p86 on the growth of short, taxol-stabilized maize microtubules were investigated. Pure microtubules underwent a gradual length redistribution, an increase in mean length, and a decrease in number concentration consistent with an end-to-end annealing mechanism of microtubule growth.

Function of the p86 subunit of eukaryotic initiation factor (iso)4F as a microtubule-associated protein in plant cells.

The isozyme form of eukaryotic initiation factor 4F [eIF-(iso)4F] from wheat germ is composed of a p28 subunit that binds the 7-methylguanine cap of mRNA and a p86 subunit having unknown function. The p86 subunit was found to have limited sequence similarity to a kinesin-like protein encoded by the katA gene of Arabidopsis thaliana. Native wheat germ eIF-(iso)4F and bacterially expressed p86 subunit and p86-p28 complex bound to taxol-stabilized maize microtubules (MTs) in vitro.

Deficient nucleation during co-polymerization of mammalian MAP2 and tobacco tubulin.

To obtain information on the functional domains of tubulin from a dicot plant, we investigated the interactions of tobacco tubulin with MAP2 from bovine brain supernatant. Taxol-stabilized tobacco and bovine brain microtubules had similar binding capacities for MAP2 (1 mol MAP2 per 8-9 mol tubulin). However, MAP2 dissociated from tobacco microtubules more readily than from bovine brain microtubules and induced the polymerization of tobacco tubulin into aberrant helical ribbon polymers, rather than microtubules.

Competitive Inhibition of High-Affinity Oryzalin Binding to Plant Tubulin by the Phosphoric Amide Herbicide Amiprophos-Methyl.

Amiprophos-methyl (APM), a phosphoric amide herbicide, was previously reported to inhibit the in vitro polymerization of isolated plant tubulin (L.C. Morejohn, D.