The two divergent PEP-carboxylase catalytic subunits in the green microalga Chlamydomonas reinhardtii respond reversibly to inorganic-N supply and co-exist in the high-molecular-mass, hetero-oligomeric Class-2 PEPC complex.
Our recent molecular studies revealed two divergent PEP-carboxylase (PEPC [Ppc]) encoding genes in the green microalga Chlamydomonas reinhardtii, CrPpc1 and CrPpc2, which are coordinately responsive to changes in inorganic-N and -C supply at the transcript level [Mamedov, T.G., Moellering, E.R. and Chollet, R. (2005) Identification and expression analysis of two inorganic C- and N-responsive genes encoding novel and distinct molecular forms of eukaryotic phosphoenolpyruvate carboxylase in the green microalga C. reinhardtii, Plant J. 42, 832-843]. Here, we report the distribution of these two encoded catalytic subunits in the minor Class-1 and predominant Class-2 PEPC enzyme-forms, the latter of which is a novel high-molecular-mass, hetero-oligomeric complex containing both CrPpc1 (p109) and CrPpc2 (p131) polypeptides. The Class-1 enzyme, however, is a typical PEPC homotetramer comprised solely of p109. We also document that the amount of both CrPpc1/2 catalytic subunits is up-/down-regulated by varying levels of NH(4)(+) supplied to the culture medium.
Moellering
Eric R
ER
Department of Biochemistry, University of Nebraska-Lincoln, George W. Beadle Center, Lincoln, NE 68588-0664, USA.
Ouyang
Yexin
Y
Mamedov
Tarlan G
TG
Chollet
Raymond
R
D020418:Algal Proteins / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D000818:Animals; D000918:Antibody Specificity; D020134:Catalytic Domain; D016825:Chlamydomonas reinhardtii / Q000201:enzymology*; D003470:Culture Media; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D015151:Immunoblotting; D010730:Phosphoenolpyruvate Carboxylase / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D011489:Protein Denaturation; D021122:Protein Subunits / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D003313:Zea mays / Q000201:enzymology
D020418:Algal Proteins; D003470:Culture Media; D021122:Protein Subunits; D000644:Quaternary Ammonium Compounds; D010730:Phosphoenolpyruvate Carboxylase