
%0 Journal Article
%A Li, Bin 
%A Pacquit, Valérie 
%A Jiao, Jin-an 
%A Duff, Stephen M.G. 
%A Maralihalli, Gururaj B. 
%A Sarath, Gautam 
%A Condon, Shirley A. 
%A Vidal, Jean 
%A Chollet, Raymond 
%T Structural Requirements for Phosphorylation of C<emph tye="8">4</emph>-Leaf Phospho<emph type="2">enol</emph>pyruvate Carboxylase by its Highly Regulated Protein-Serine Kinase. A Comparative Study with Synthetic-Peptide Substrates and Mutant Target Proteins
%J Functional Plant Biology
%D 1997/11/19
%V 24
%N 4
%P 443-449
%K 
%R https://doi.org/10.1071/PP97009
%U https://www.publish.csiro.au/paper/PP97009 
%X A family of synthetic peptides modelled after the highly conserved, N-terminal phosphorylation domain of C4 phosphoenolpyruvate carboxylase (PEPC) and a complementary set of recombinant mutant target proteins were exploited to investigate the local structural requirements for phosphorylation of this cytosolic C4 enzyme by its Ca2+-independent protein kinase. The only peptide homolog examined that was significantly phosphorylated by maize (Zea mays L.) leaf PEPC-kinase spanned the P&#8722;5 through P+16 region surrounding the target serine residue in maize PEPC (fifth through sixteenth residues on the N- and C-terminal sides, respectively, of the phosphorylatable serine at position &#8216;P&#8217;). However, its apparent Km value was 200-times that of intact C4 PEPC. The results from the related site-directed mutagenesis experiments with the recombinant sorghum (Sorghum vulgare) C4 -enzyme indicated that alteration of several highly conserved residues flanking the target serine with non-conservative Ala substitutions at the P&#8722;4, P&#8722;3, and P+10 positions had only modest effects, if any, on its in-vitro phosphorylation by maize PEPC-kinase. These collective findings implicate a secondary site(s) of interaction in C4 PEPC, removed from the N-terminal phosphorylation domain, that is also an important recognition element for its low abundance, highly regulated protein-serine/threonine kinase. 
