POSTTRANSLATIONAL MODIFICATIONS IN THE AMINO-TERMINAL REGION OF THE LARGE SUBUNIT OF RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE OXYGENASE FROM SEVERAL PLANT-SPECIES

A combination of limited tryptic proteolysis, reverse phase-high perfo rmance liquid chromatography, Edman degradative sequencing, amino acid analysis, and fast-atom bombardment mass-spectrometry was used to rem ove and identify the first 14 to 18 N-terminal amino acid residues of the large subunit of higher plant-type ribulose-1,5-bisphosphate carbo xylase/oxygenase (Rubisco) from Chlamydomonas reinhardtii, Marchantia polymorpha, pea (Pisum sativum), tomato (Lycopersicon esculentum), pot ato (Solanum tuberosum), pepper (Capsicum annuum), soybean (Glycine ma x), petunia (Petunia x hybrida), cowpea (Vigna sinensis), and cucumber (Cucumis sativus) plants. The N-terminal tryptic peptide from acetyla ted Pro-3 to Lys-8 of the large subunit of Rubisco was identical in al l species, but the amino acid sequence of the penultimate N-terminal t ryptic peptide varied. Eight of the 10 species examined contained a tr imethyllysyl residue at position 14 in the large subunit of Rubisco, w hereas Chlamydomonas and Marchantia contained an unmodified lysyl resi due at this position.