Absolute quantification of Medicago truncatula sucrose synthase isoforms and N-metabolism enzymes in symbiotic root nodules and the detection of novel nodule phosphoproteins by mass spectrometry

Author(s)

Stefanie Wienkoop, Estibaliz Larrainzar, Mirko Glinski, Esther M. Gonzalez, Cesar Arrese-Igor, Wolfram Weckwerth

Abstract

Mass spectrometry (MS) has become increasingly

important for tissue specific protein quantification at

the isoform level, as well as for the analysis of protein

post-translational regulation mechanisms and turnover

rates. Thanks to the development of high accuracy

mass spectrometers, peptide sequencing without prior

knowledge of the amino acid sequence—de novo

sequencing—can be performed. In this work, absolute

quantification of a set of key enzymes involved in

carbon and nitrogen metabolism in Medicago truncatula

‘Jemalong A17’ root nodules is presented. Among

them, sucrose synthase (SuSy; EC 2.4.1.13), one of the

central enzymes in sucrose cleavage in root nodules,

has been further characterized and the relative phosphorylation

state of the three most abundant isoforms

has been quantified. De novo sequencing provided

sequence information of a so far unidentified peptide,

most probably belonging to SuSy2, the second most

abundant isoform in M. truncatula root nodules. TiO2-

phosphopeptide enrichment led to the identification of

not only a phosphorylation site at Ser11 in SuSy1, but

also of several novel phosphorylation sites present in

other root nodule proteins such as alkaline invertase

(AI; EC 3.2.1.26) and an RNA-binding protein.

Organisation(s)

External organisation(s)

Universidad Pública de Navarra, Idea AG

Journal

Journal of Experimental Botany

Volume

Pages

3307-3315

No. of pages

ISSN

0022-0957

Publication date

2008

Peer reviewed

Yes

Austrian Fields of Science 2012

106002 Biochemistry, 1030 Physics, Astronomy, 106037 Proteomics, 106031 Plant physiology

Portal url