Molecular characterization of poly(A)-binding protein from Daucus carota.

Poly(A)-binding proteins (PABs) bind to the poly(A) tails of most eukaryotic mRNAs and thereby influence the translational efficiency as well as the stability of the mRNAs thus bound. Compared with the data on yeast PAB, relatively little is known about the functions of PABs in higher plants. The cDNA encoding PAB was cloned by the method of "virtual subtraction" from carrot somatic embryos cultured with different sucrose concentrations. Sequence alignment reveals a significant homology between the deduced amino acid sequence of DcPAB and those of other PABs. The deduced sequence consists of 658 amino acids with a calculated molecular weight of 71.9 kDa. The cDNA has been expressed as a recombinant protein in Escherichia coli. The differential expression of DcPAB under different conditions suggests a potently unique role in the development of carrot somatic embryo.