Phytosulfokine-alpha, a peptide growth factor found in higher plants: Its structure, functions, precursor and receptors

Phytosulfokine-alpha, a sulfated pentapeptide growth factor universally fou nd in both monocotyledons and dicotyledons, strongly promotes proliferation of plant cells in culture. It is similar to animal polypeptide hormones in that it is processed from a larger precursor, preprophytosulfokine, althou gh the putative processing sites do not conform to consensus sequences for endoproteolytic processing sites flanking animal prohormones, Like the anim al preprohormones, preprophytosulfokine also has a signal peptide at the N- terminus for targeting to secretory pathways. The preprophytosulfokine gene has been confirmed to be expressed in vivo as well as in vitro.