title: Post-translational modifications in the large subunit of ribulose bisphosphate carboxylase/oxygenase.
abstract: Two adjacent N-terminal tryptic peptides of the large subunit of ribulose bisphosphate carboxylase/oxygenase [3-phospho-D-glycerate carboxy-lyase (dimerizing), EC 4.1.1.39] from spinach, wheat, tobacco, and muskmelon were removed by limited tryptic proteolysis. Characterization by peptide sequencing, amino acid composition, and tandem mass spectrometry revealed that the N-terminal residue from the large subunit of the enzyme from each plant species was acetylated proline. The sequence of the penultimate N-terminal tryptic peptide from the large subunit of the spinach and wheat enzyme was consistent with previous primary structure determinations. However, the penultimate N-terminal peptide from the large subunit of both the tobacco and muskmelon enzymes, while identical, differed from the corresponding peptide from spinach and wheat by containing a trimethyllysyl residue at position 14. Thus, tryptic proteolysis occurred at lysine-18 rather than lysine-14 as with the spinach and wheat enzymes. A comparison of the DNA sequences for the large subunit of ribulose bisphosphate carboxylase/oxygenase indicates that the N terminus has been post-translationally processed by removal of methionine-1 and serine-2 followed by acetylation of proline-3. In addition, for the enzyme from tobacco and muskmelon a third post-translational modification occurs at lysine-14 in the form of N epsilon-trimethylation.
authors.affiliation: Department of Horticulture and Landscape Architecture, University of Kentucky, Lexington 40546.
authors.forename: R L
authors.initials: RL
authors.lastname: Houtz
authors.forename: J T
authors.initials: JT
authors.lastname: Stults
authors.forename: R M
authors.initials: RM
authors.lastname: Mulligan
authors.forename: N E
authors.initials: NE
authors.lastname: Tolbert
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D002851:Chromatography, High Pressure Liquid; D005638:Fruit; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000378:metabolism; D010944:Plants / Q000201:enzymology*; D010947:Plants, Toxic; D011499:Protein Processing, Post-Translational; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism*; D014026:Nicotiana; D014908:Triticum; D014357:Trypsin / Q000378:metabolism; D014675:Vegetables
chemical_list: D000596:Amino Acids; D010446:Peptide Fragments; D014357:Trypsin; D012273:Ribulose-Bisphosphate Carboxylase