Interaction of PRK1 Receptor-like Kinase with a Putative eIF2B β-Subunit in Tobacco.

PRK1, a receptor-like kinase that is expressed in pollen, pollen tubes, and ovaries, has been shown to play important roles in pollen development and embryo sac development in Petunia inflata. We have used the kinase domain of PRK1 as a bait in the yeast two-hybrid system to identify PRK1-interacting proteins. The screening resulted in isolation of a cDNA encoding a protein highly homologous to the human and yeast beta-subunit of translation initiation factor 2B (e1F2B-beta), which was designated NeIF2B beta. e1F2B is a guanine nucleotide exchange protein that functions in the regulation of translation in eukaryotic cells. Deletion mutants of NeIF2B beta were analyzed for their interaction with PRK1, and the results suggested that the N-terminal half of NeIF2B beta, especially the region between residue 103 and 235, is important for the interaction. This protein association was confirmed by in vitro binding assay of the recombinant NeIF2B beta and PRK1 proteins. Despite high sequence homology between NeIF2B beta and its yeast counterpart, the NeIF2B beta cDNA could not rescue the phenotype of the yeast mutant strain lacking the GCD7 gene encoding e1F2B-beta, when transferred into the mutant strain. [ABSTRACT FROM AUTHOR]