title: A chenopod extensin lacks repetitive tetrahydroxyproline blocks.
abstract: An extensin isolated from sugar beet (Beta vulgaris) cell suspension cultures fulfills all criteria for membership of the extensin family save one, notably, lack of the ;diagnostic' pentamer Ser-Hyp-Hyp-Hyp-Hyp. However, sequence analysis of the major tryptic peptides shows that sugar beet extensin shares a motif in common with tomato extensin P1 but differs by the position of an insertion sequence [X] or [Y] which, in sugar beet, splits the tetrahydroxyproline block: Ser-Hyp-Hyp-[X]-Hyp-Hyp-Thr-Hyp-Val-Tyr-Lys, where [X] is [Val-His-Glu/Lys-Tyr-Pro], while in tomato the insertion sequence [Y] = [Val-Lys-Pro-Tyr-His-Pro] and, when it occurs, immediately follows the tetrahydroxyproline block: Ser-Hyp-Hyp-Hyp-Hyp-[Y]-Thr-Hyp-Val-Tyr-Lys. Based on these data we reinterpret three highly repetitive cDNA sequences, including nodulin N75 from soybean and wound-induced P33 of carrot, as extensins with split tetra(hydroxy)proline blocks.
authors: D.O.E. Plant Research Laboratory and Department of Biochemistry, Michigan State University, East Lansing, Michigan 48824.
authors: X B
authors: XB
authors: Li
authors: M
authors: M
authors: Kieliszewski
authors: D T
authors: DT
authors: Lamport