Potential for interactions between the carboxy- and amino-termini of Rubisco activase subunits.
The subunit interactions of Rubisco activase were investigated using mutants containing an introduced Cys near the N- and/or C-terminus. Chemical cross-linking of the C-terminal and double insertion mutant produced subunit dimers and dimers plus high ordered oligomers, respectively. Fluorescence measurements with N,N'-dimethyl-N-(iodoacetyl)-N'-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)ethylenediamine showed that the environment around the introduced Cys near the C-terminus becomes more hydrophilic upon nucleotide binding. The Cys insertion mutants catalyzed Rubisco activation and ATP hydrolysis even when the subunits of the C-terminal or double insertion mutants were completely cross-linked. The results indicate that the termini of adjacent activase subunits are in close proximity and can be modified and even joined without affecting enzyme function.
US Department of Agriculture, Agricultural Research Service, Western Cotton Research Laboratory, 4135 E. Broadway Road, Phoenix, AZ 85040-8803, USA. msalvucci@wcrl.ars.usda.gov
Michael E
ME
Salvucci
D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001483:Base Sequence; D002384:Catalysis; D003432:Cross-Linking Reagents / Q000737:chemistry; D003545:Cysteine / Q000378:metabolism; D019281:Dimerization; D004789:Enzyme Activation; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D016254:Mutagenesis, Insertional; D010940:Plant Proteins / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D013329:Structure-Activity Relationship
D003432:Cross-Linking Reagents; D010940:Plant Proteins; D021122:Protein Subunits; D011994:Recombinant Proteins; C054765:rca protein, plant; D000255:Adenosine Triphosphate; D003545:Cysteine