Phosphorylation of barley and wheat phospholipid transfer proteins by wheat calcium-dependent protein kinase

G. M. Neumann, R. Condron, Birte Svensson, G. M. Polya

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Wheat (Triticum aestivum L.) germ Ca2+-dependent protein kinase (CDPK) phosphorylates a wheat basic protein (WBP) which is a putative phospholipid transfer protein and one of the best protein substrates yet found for wheat CDPK. Reversed phase high performance liquid chromatography (HPLC) of the tryptic digest of [P-32]phospho WBP resolved two [P-32]phosphopeptide peaks. Edman sequencing of one of these established that WBP is phosphorylated by CDPK on S17 within the sequence (APCISYA)-P-13. WBP may also be phosphorylated at an additional site. Wheat CDPK also phosphorylates barley (Hordeum. vulgare) lipid transfer protein (LTP1) and [P-32]phosphoLTP1 exactly comigrates with LTP1 on SDS-PAGE. Unlike wheat WBP, LTP1 is a relatively poor substrate for wheat CDPK and is phosphorylated largely on threonine. Reversed phase high performance liquid chromatography (HPLC) of the tryptic digest of [P-32]phosphopeptide resolved one [P-32]phosphopeptide and subsequent Edman sequencing of this phosphopeptide showed that LTP1 is phosphorylated on T15 within the sequence (KPCLTYVQ)-P-11. This phosphorylation site amino acid sequence motif differs from the Basic-X-X-Ser(Thr) motif found for a variety of synthetic peptide substrates of wheat germ CDPK but corresponds to the Pro-Cys-X-Ser/Thr phosphorylation site motif found for the phosphorylation by wheat germ CDPK of WBP, which is a homologue of barley LTP1. The phosphorylation sites determined for WBP and LTP1 are similar structurally and are within precisely aligned homologous sequences.
Original languageEnglish
JournalPlant Science
Volume92
Issue number2
Pages (from-to)159-167
ISSN0168-9452
DOIs
Publication statusPublished - 1993
Externally publishedYes

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